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Miles-Per-Gallon Is Just Stupid. No, Really, It Is.

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Americans aren't stupid. We're just badly informed. And occasionally, stubborn.

Why else would we ignorantly cling to using miles per gallon as the way to measure how efficiently a car uses fuel?

But maybe you don't quite see the problem. OK, so here's a little test:  Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg?

If you're like most Americans, you picked the second one. But, in fact, that's exactly backwards. Over any given mileage, replacing a 10-mpg vehicle with one that gets 20 mpg saves five times the gasoline that replacing a 33-mpg vehicle with one that gets 50 does.

Don't believe it? Here’s the math. If you replace your old 1990s SUV (10 mpg) with a new 2009 Chevrolet Tahoe Hybrid (20 mpg), over 100 miles you cut your gasoline consumption from 10 gallons to 5. That saves you five gallons.

If you swap your old Toyota Echo (33 mpg) for a new 2011 Toyota Prius (50 mpg), that only saves you one single gallon over the same distance--down from 3 to 2 gallons.

2010 Toyota Prius

2010 Toyota Prius

Enlarge Photo

Yes, the Prius uses less gasoline overall, and that's absolutely greener. But like it or not, lots and lots and lots of Americans need large vehicles for their jobs, their families, and their lives. Short of truly punitive taxes on vehicle weight, footprint, or engine size, that won't quickly change.

In other words, we could cut our petroleum imports, reduce our carbon output, green the planet, and all act like happy bunnies if we replaced all our truly low-mileage "guzzlers" (we're thinking 1978 Chrysler Brougham or, hey, late-1990s Chevy Suburban) with vehicles that get just 20 miles per gallon.

That'd save a whole lot more actual gasoline than, say, replacing 3 percent of vehicles sold in the US with hybrids. Which is exactly what we've done over 10 years. In fact, US average mileage has pretty much stalled as vehicles have gotten larger, heavier, and better equipped.

This has led to all sorts of misconceptions, including the impact of the Corporate Average Fuel Economy (CAFE) regulations now being written. We actually think that higher gas taxes are a smarter way to let the market sort out what fuel consumption it will pay for, but we're not going there. (This time.)

2009 Chevrolet Tahoe Hybrid

2009 Chevrolet Tahoe Hybrid

Enlarge Photo

So that's the problem: Americans can't accurately work out how to save the most gasoline. What's the solution? Simple. Measure fuel usage the way the entire rest of the world (including Canada) does: consumption over distance. There, it's mostly liters per 100 km. Here, it'd be gallons per 100 miles.

Do you know all this and just do the math in your head? Well, you're way ahead of the curve. (Test yourself first, though...) A few years ago, Duke University’s Fuqua School of Business released a study that shows how much damage comes from using MPG instead of consumption to measure how green a car is.

Management professors Richard Larick and Jack Soll's experiments proved that consumers thought fuel consumption was cut at an even rate as mileage increased. Most survey respondents said going from 34 to 50 mpg saved more gasoline over 10,000 miles than did moving from 18 to 28 mpg. Their website, "The MPG Illusion," lays out the whole issue.

There are now a few moves toward putting consumption on window stickers, right next to mileage. And when both a Midwestern Republican Congressman and The New York Times agree on something, it's gotta have some merit, right?

That way, you could compare the Corolla's 3 gallons every 100 miles against the Prius's 2, calculate the extra cost, and decide if you wanted to make that Prius statement after all. For 8,000 miles a year, on $2/gallon gas, by the way, the gas will cost you $160 a year more.

But, hey, Americans are stubborn. We beat back the metric system, right? Consumption instead of mileage? Nah. Dumb idea. Never work. [sigh]

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Comments (112)
  1. "What about that car that does 70mpg?"

    Screw hybrids. What I don't understand is why we think hybrids are so damned efficient when there are cars overseas that get 50-70mpg. I'll tell you why - diesel. For some reason Americans would rather ravage the world by producing NiMH batteries in a Prius (that gets less than 50mpg) than drive a small engined diesel that gets 70mpg.
    I don't get it.
     
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  2. "waste of time"

    This article was a waste of time. Your pathetic attempt at stating your math formula works is the worse example ever. You'd have to cross-compare every car and your formula would both work and fail. Why was this even posted?
     
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  3. "shut up"

    shut up, you're retarded.
     
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  4. "Rockstar"

    I beg to differ with the opening statement: "Americans aren't stupid." In general, and as compared to the other nations of the world, Americans are pretty stupid. Your education system is poor and any time anyone mentions socialism, half the populace starts burning Soviet flags and trying to kill anyone who thinks that subsidized child care for single moms is a good idea should be shot (with my M249 "hunting" machine gun).
     
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  5. "GREAT ARTICLE, IDIOT"

    This is the stupidest logic I've ever heard! While 10-20 saves more fuel... getting 50mpg saves more fuel than any other MPG lower... if a family needs 2 cars, one of which gets worse mileage, they benefit by selecting the 2 cars with the highest fuel mileage that meet their needs! Who needs to know consumption when it's a number that can be calculated using MPG, are you saying that selecting the vehicle that meets your needs that has the highest MPG is stupid and in some way doesn't work?
     
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  6. "Go Back to 5th Grade."

    I wish you knew how to do math. Percent difference does not equal (or trump) absolute consumption. You're a fool.
     
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  7. "Go Back to 5th Grade."

    I wish you knew how to do math. Percent difference does not equal (or trump) absolute consumption. You're a fool.
     
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  8. "Go Back to 5th Grade."

    I wish you knew how to do math. Percent difference does not equal (or trump) absolute consumption. You're a fool.
     
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  9. "Math literacy"

    The root problem is math literacy, not the way we calculate fuel consumption
     
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  10. "Actually, Tim ..."

    ... this is a question we get quite a lot here, and it's probably worth doing a story on.
    Short answer: Most of the small Eurodiesels are too dirty to be sold in the US, which has the most stringent emissions standards for particulates in the world.
    And, the European manufacturers who were confidently touting diesels for the US as the way to go are a lot less confident right now, with diesel significantly pricier than gasoline.
    Does that help answer your question?
     
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  11. There is also the slight detail that in the EU the MPG claims are much more dubious. The 5 cycle test used to determine MPG in the US is much more accurate and actually represents roughly what a normal driver would see as their mileage. An EU driver would likely have quite a difficult time matching their stats in everyday use!
     
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  12. "You are stupid"

    10mpg to 20 mpg. 10/5 gallons to go to 100.
    33 to 50 mpg. 3.3/2 gallons to go to 100. I believe that is where the gas savings comes from. not from your twisted logic
     
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  13. "whats with your logic"

    no wonder why americans fck'd up the economy ...
     
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  14. "What are you talking about"

    It's a linear scale. Any amount of savings is better than the last. The 33-50 is a far better saving than 10-20 since 7 more gallons are saved per mile. There is no magic here. The person who is driving a 10mpg vehicle should be embarrassed to be paying that much for fuel - and you should be embarrassed for over-complicating the math.
     
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  15. "Really?"

    Really? It sounds like a convoluted way to describe something like miles per gallon. The problem isn't that MPG is necessarily a bad measuring system, it's that people don't know what MPG means. A simple understanding of what it means and you can see that 10 to 20 is double the miles.
    So maybe making that drivers ed. class mandatory would be a better solution.
     
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  16. "WoW"

    YOUR LOGIC IS HILARIOUS
     
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  17. "Miles per gallon vs consumption."

    While both measures have merit, the argument that miles per gallon is not a valid measure is flawed. Citing issues with people not understanding the math involved is really only pointing towards this article trying to say its ok to have cars that guzzel gas because hey 20 MPG is better than 10 right... right?
     
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  18. "Miles per gallon vs consumption."

    While both measures have merit, the argument that miles per gallon is not a valid measure is flawed. Citing issues with people not understanding the math involved is really only pointing towards this article trying to say its ok to have cars that guzzel gas because hey 20 MPG is better than 10 right... right?
     
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  19. "Americans arent stupid"

    Congratz you prove this statment wrong.
     
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  20. "Actually, Tim ..."

    ... this is a question we get quite a lot here, and it's probably worth doing a story on.
    Short answer: Most of the small Eurodiesels are too dirty to be sold in the US, which has the most stringent emissions standards for particulates in the world.
    And, the European manufacturers who were confidently touting diesels for the US as the way to go are a lot less confident right now, with diesel significantly pricier than gasoline.
    Does that help answer your question?
     
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  21. "?????"

    This is retarded logic. Why not then just go from 10 to 50? And any increase in mpg is great. When that little fuel efficiency improvement is multiplied by millions, the effect is no more negligible. You sound just like the stupid American, you say the article is aimed at. Mpgs should be compared in absolute terms, not comparative. If you can afford it, get a vehicle with as high mpg as you can. -German
     
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  22. "Balderdash"

    Don't blame the effects of laziness and lack of education on the scientific units. Implying that somehow I have a harder time telling the difference between 34mpg and 50mpg vs 6.9 and 4.7L/100km respectively is a little hard to swallow. Really, now which looks like a bigger difference: +16 or -2.2? And when we get to 100mpg, do you really think that L/100km has enough resolution left? Let's see: going from 100mpg to 105 mpg is the same as 2.35 to 2.24L/100km, respectively. How is this better?
     
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  23. "Market percentage of vehicles"

    You also have to consider the market percentage which the type of vehicle holds in the consumer market. While you do say a lot of Americans need specific vehicles for specific task, you have to consider what that is compared the market share of total vehicle ownership.
    continued below:
     
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  24. "Mr."

    "There are 3 kinds of lies: Lies, damn lies, and statistics." (The origin of this quote is disputed.)
    And this article is just a pointless math trick.
     
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  25. "..continued"

    So if sedans hold 3x the market share of trucks then the gas saving by only gaining 2 mpg higher overall compared to the 5mpg in trucks (2x3=6 5) could in turn return higher gas savings overall.
    However, this whole topic is pretty much a moot point anyways, the idea is we should replace "ALL" vehicles with higher mpg regardless of which market segment they are in.
    I do agree using mpg to compare across segments is foolish, I just think your topic needs to make that point a bit clearer.
     
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  26. "Balderdash Pt.2."

    I would have written more, but a 500 character limit means that only vitriol can come through, not intelligent debate.
     
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  27. "More Math"

    Would you rather buy one gallon of gas and get an extra 10 miles per gallon (20 - 10) or an extra 17 miles (50 - 33)? Although I am not getting double what I had before, I am getting more out of the money that I am spending on gas.
    The fact is, even if the second person does not upgrade his car, he is using less gas at 33 mpg than the first person is by upgrading to 20 mpg.
     
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  28. "so, Lex ..."

    ... you're saying, "The 33-50 is a far better saving than 10-20 since 7 more gallons are saved per mile."
    REALLY?
    So every mile I drive in that 50 mpg car, I've saved 7 MORE gallons? You think so?
    Not true, I'm afraid. What really scares me--as one commenter points out here--is the remarkable lack of math skills amongst (apparently many) Americans. Wow.
     
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  29. "Say What?"

    The author recommends measuring gallons consumed per so many miles as an alternative to MPG? Wouldn't that just basically be the inverse of MPG? Maybe it'd help make the math easier when estimating the cost of gas over a year, but that doesn't help the claim about American intelligence. Consumers compare what they currently drive to what they're thinking of buying, and in that case the higher MPG is always better.
     
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  30. "Big Oil Propaganda"

    Please! If you believe that continuing with the same old ICE (Internal Combustion Engine) paradigm is greening the Planet, then you are... American. Just more Business As Usual And Above All Else, citizen, nothing to hope fore here, move along.
     
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  31. "Fool"

    This article is wasteful trash and has no meaning. The author wastes words and time...now off to my HUMMER BABY
     
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  32. "Sir"

    This article is fucking retarded. No offense to the mentally disabled.
     
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  33. "Stranger that fiction"

    Come on, anyone can write a blog, try proof reading before posting. I'm not an english major, but if you are trying to be an authority, check your spelling and grammar.
     
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  34. "Good points / Bad message"

    Why do people think the Prius's only draw is MPG? Its technologically advanced in just about every other way, too. So feel free to call me a hippy, while you drive around happy in your American-designed POS.
     
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  35. "What an annoying article"

    Gallons per mile is a better indication of cost for the consumer (as most of us know how many miles we travel in a year), but your trick question should not be used as a justification for changing mpg to gpm.
    If you asked them, "Which has a higher percentage improvement in gas mileage", well then they'd get the answer correct of course, as the question is more clear!
     
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  36. "retired"

    Another interesting automotive article in a long history of interesting automotive foolishness.
    We are striving and legislating to eliminate the gas hogs, not give reasons by sleight-of-hand tricks, for keeping them around.
    Your math is impeccable you just missed that 1200 lb. PIG in your living room...the one painted purple son.
     
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  37. "Editor-in-Chief?"

    This whacko is Editor-in-Chief? Certainly says a lot for the rest of the paper doesn't it? I can just see him sitting around sipping a smoothie and justifying himself to his bored wife and friends.
     
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  38. "Article-fail, Comments-not so much"

    At first I was pissed that I wasted my time reading this post. Then I read the other comments and that made it worthwhile.
     
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  39. "Older vehicles that get the same mileage"

    Honestly, i dont see why ppl are going to hybrids, my 98 Dodge Ram 1500 gets anywhere from 18-22 mpg, and my Geo metro gets anywhere between 48-53 mpg plus not to mention cost of repairs... my vehicles are cheeper to fix than a hybrid.
     
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  40. The scathing responses only show that many eco-minded consumers are sheep, just as stubborn and dogmatic as their right-wing opponents.
    Think about this article for two seconds and the math checks out. It doesn't mean that Priuses do less good than Escalade Hybrids. It means that we hybrid the SUVs as much as the small cars. Lexus knows this, and *gasp* so does GM.
     
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  41. Watch out Ben we have a new Fed man in your future.I know I am not the smartest guy in town but I pay the bill for a hundred mile trip, in a 50 mpg vehicle and you pay the bill in a 20 mpg vehicle and I darn sure know I will spend less than the educated writer of this article.
     
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  42. I have no real opinion on the matter due to the fact that a cars fuel consumption has many different factors. The location of the car (City/Suburbs/Country Side), The operating Temperature (Colder temps generally hurt MPG), Altitude of the location, etc.
    However, the pig headed comments that people leave here are the most disturbing. They have completely missed the point of John’s article. I guess most of the commenters have never attended school higher than 5th grade. They have somehow ascertained the limited knowledge to turn on a computer and leave comments on a blog. But are incredibly inept when it comes to manners, and using constructive criticism. My guess most of the "Shut Up" "Retard" "Idiot" comments come from the same people who think Bill O'Reilly is god and in that case should be feed to a pack of starving wolves.
     
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  43. We have been dealing with the L/100km crap up here for a while now and all I can say is, it blows. As soon as I saw this new rating I knew it was the auto industry pushing this crap. km/L is a much better way to do it (like MPG) because it's a tangible value that you can visualize in your head.
    How much is a Litre (gallon), oil (milk) comes to mind, how far can I go? My sister lives 10km away (next town is 30miles away), that's how far I can go. If I get a car that gets 45mpg I can now come half way back again on that same gallon.
    It's definately a slight if hand, non-tangable way fo looking at it.
     
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  44. "Would you rather buy one gallon of gas and get an extra 10 miles per gallon (20 - 10) or an extra 17 miles (50 - 33)?"
    This is *exactly* the problem that the article was attempting to highlight. It doesn't matter in the slightest how far you can go on one gallon of gasoline (aside from minimizing stops at the gas station, which also depends on the size of your tank). Your trip length is constant, regardless of fuel economy, so what you care about is how much gas you need to make that trip. For a constant distance, say 100 miles, you save more fuel and cost by going from 10 MPG to 20 MPG (10 gallons vs. 5 gallons) than you would save by going from 33 MPG to 50 MPG (3 gallons vs. 2 gallons). This is in both relative (50% vs. 33%) and absolute (5 gallons vs. 1 gallon) terms.
    There is no point in saying that people should buy 50 MPG vehicles instead of 20 MPG vehicles; these are entirely different types of vehicles with different cargo and tow capacities. With very few exceptions, you can't replace existing full-size trucks with subcompact cars. However, you may be able to replace older 10 MPG trucks with new 20 MPG trucks with similar characteristics, for much greater fuel savings than you'd get by upgrading already-efficient small vehicles.
     
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  45. This article is spot on - as is illustrated by the comments here. Look at Lex's comment:
    "It's a linear scale. Any amount of savings is better than the last. The 33-50 is a far better saving than 10-20 since 7 more gallons are saved per mile. There is no magic here."
    There is indeed no magic here - just an error. The statement that "7 more gallons are saved per mile" is simply false. Look at your statement, and calculate the amount of gas for a 100 mile trip. Or reread the article.
     
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  46. I find it funny that the writer of this article flaunts his assumed superiority for understanding something that he in fact has ass backwards.
    It's not a measurements of how much gas you save over a given distance. It's measured linearly in gas/distance.
    Would you rather get 17 more miles out of every gallon you pay a fixed amount of money for or 10?
    This is the same logic:
    Would you rather hand someone $10 and have them hand $20 back or hand them $33 and get $50 back?
    According to this idiot's logic, the first option is best because 20/10 50/33.
    As an american, I hope that John Voelcker is not one.
     
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  47. Re: "Americans aren't stupid"
    Reading some of these comments... I'm not so sure.
    PS: The article is correct.
     
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  48. I promise all us American's are not as stupid as the people posting here...
    Article makes perfect sense. Math is perfect and the logic behind it is sound.
    1 mpg to 2 mpg is a bigger savings than 2 mpg to 100 mpg ;)
     
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  49. No David, you have it backwards. Say you drive 100 miles a week, and gas costs $1. If you get 10mpg you spend $10. If you get 20mpg you spend $5. If you get 33mpg you spend $3, if you get 50mpg you spend $2. So by going from 10 to 20 mpg you save $5 a week, while going from 33 to 50mpg saves you $1 a week.
     
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  50. The comments so far prove the point as much as anything. The math isn't _wrong_ even if you don't like the idea itself.
    Math aside, I like the system proposed. It is better for comparing vehicles fuel consumption rather than range. This is usually more important for buying cars.
    To borrow from another poster on another website:
     
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  51. I do not get how MPG is stupid. As you say in your article the higher mpg cars save more fuel. Yes it is a relative thing, if you have a car that gets 1 mpg then replacing it with one that gets 2 mpg would save 50 gallons over 100 miles, but that does not mean you should avoid the car that gets 100 mpg saving 99 gallons. I think you would have made a much more convincing argument if you showed the difference related to manufacturing.
     
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  52. article is intentionally misleading, or rather the source is. there's a big difference between SAVINGS and actual gasoline use. 10-20MPG is *halving* gas usage. 33-50 is merely 1/3 the usage. so of course 10-20 *saves* more gas over the same distance. you could just as easily say 1-2MPG saves more gas -- because it does. the *savings* is only net from the *original* figure, not overall.
    look at it another way: which saves more gas, 10-50MPG or 33-50 MPG. duh, 10-50, but only because you are starting from a much worse position. but at the end of the day you are consuming the same amount of gas for both cars.
    MPG is a perfectly valid comparison between cars.
     
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  53. Give someone $10 and get $20 back, or give someone $33 and get $50 back?
    The first option is best, I'm afraid. If you do it three times, you've given $30 and gotten $60 back.
    (Yes, it is related to the topic of gas consumption, but that explanation is left as an exercise to the reader -- not because it's difficult, but because I hope it'd be bloody obvious.)
     
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  54. this is a simple math puzzle (like how many triangles are in this figure) mis-used for someone's pet consumption argument.
    here's another way to look at it. which is better, going from 10-20MPG, or starting from 33MPG and staying there. going from 10-20 *saves* more ... obviously, since starting at 33 and staying at 33 saves *nothing*. but which would you rather have?
     
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  55. driving 100 miles at 1mpg uses 100 gallons. at 2 mpg it uses 50 gallons. at 100mpg it uses 1 gallon. So you save about the same amount of gas (around 50 gallons for each 100 miles you drive) going between each efficiency point.
     
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  56. @cash tree: you are an idiot. let's trade, i'll give you $33 and you give me $50, then you give me $10 and I'll give you $20.
    i'll net $3 for each transaction.
     
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  57. What this article doesn't mention, is the rare earth elements required by the batteries that hybrids require. The "20 mpg " Surburban takes alot of batteries! The rare earth elements come from China, and Chinese mines are not exactly known for being environmentally friendly.
     
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  58. oops, i meant i'll net $7 for each trade we do.
    if you have a fixed amount of money to start, yes of course doubling ($10-$20) is better than 1-1/3 ($33-$50), but since we can do any number of transactions, i'll take the $50 thank you very much.
    likewise, i'd much rather have a 50MPG car than a 20MPG car.
     
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  59. Wow. First, read the article people. The question is "What Saves More", the answer to the question is "going from 10 to 20". It isn't about distance or anything like that, it is simply about the percentage improvement between two options. Of course 33 or 50 or 5000 MPG is better than 20; the problem is that this has nothing to do with the question being asked!
    John makes two great points in this article. First, that it would make more sense to explain fuel economy in terms of Gals/100miles. Yes, #42, MPG does better answer the question of "how far can I go" - unfortunately that is not a particularly useful question unless you happen to be in a place where gas stations are only every hundred miles or so. If that's your situation I'd recommend keeping a spare tank with you somehow.
    The second point John made is reinforced by the comments here. Americans are stubborn and not great at math. I'm not sure why these responses are so pointed and angry... the guy is trying to help you understand something & almost every reply is either an attack, incorrect or both. John - many reading this appreciate the article and are embarrassed by the comments.
     
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  60. I find myself conflicted because the author is using some badly mixed references. As another commenter pointed out mpg is distance based on common consumption. However John kept refering to savings. Saving and consumption are always opposite no matter how math impaired you are. Unless you are refering to consuming less I fail to understand the clearly unstated point. If we are talking about selecting between an old low mpg vehicles and a new high mpg vehicles are you saying that someone who selects a vehicle that gets more mpg is stupid? Clearly you are failing to say that you believe that people think more fuel is saved if you choose replacing a 1995 ford escort with a 2010 prius over replacing a 1985 Suburban with a 2010 Forerunner.
    Ratings are based on constants. 50 mpg means that the constant is the fuel and the measurement is the distance. Gallons per 100 miles means the distance is constant and the fuel consumed is measurement. Both ratings are valid.
    So if you could perhaps clarify what the heck are you talking about your article might start to make sense.
    If the purpose of your article is to enlighten us all I have to refer to an old teaching adage:
    "If your student can't give you the right answer perhaps you are asking the wrong question."
     
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  61. "But, hey, Americans are stubborn. We beat back the metric system, right?"
    The problem with the metric system is that its base units are completely arbitrary, and it divides poorly unless you are using the prime numbers 2 or 5. Compare the "English" system, which sticks to a base of 12 for most of its units, and thus can divide well by 2,3,4, and 6.
    Prime factorization is damned important for a system to be used day-to-day.
     
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  62. Dear John Voelcker,
    I would like to know why you choose to prove your point by picking out one commenter's casual mistake at subtracting numbers, while you ignore a very valid point made by many other commenters, namely that MPG is a utterly useful way of expressing the efficiency of fuel usage, because it reminds you that a 10 MPG car is five times less efficient than a 50 MPG car (independently what car you owned before).
    Regards,
    Maarten
     
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  63. Some people don't give a crap how much fuel they save. Fuel tanks are fixed, unlike range. They want to know how far they can go with the same amount of fuel - are we stopping in this town or carrying on to the next town to fuel up?
     
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  64. How the fu*k this did this guy became a Senior Editor? Go back to high school!
     
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  65. John, here is an idea for presenting this idea: We pay for gas in dollars per gallon, and a lot of people care about dollars per distance. We can calculate this with the current unit: ($4 per gallon)/(10 mpg) = .4 $/mi. Or we could do: ($4 per gallon) * (.1 g/mi) = (.4 $/mi). Multiplying this by the trip distance of course gives cost of the trip! (This of course is over simplifying costs just to fuel.) When arguing that we should adopt the reciprocal of the current unit, it might help if you bring people's wallets into the discussion. Just an idea.
     
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  66. Unlike many of the commenters, many of us live in the real world. People in the real world have to decide if it's smarter to replace their 10-year-old truck, or their 10-year-old Corolla. That's what this is about.
     
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  67. I am not sure gpm is psychologically acceptable. Usually bigger is considered to be better (larger numbers). A gpm of zero would ideally be the best and as you "stomp on it" it heads to maximum (99 on my Jeep).
    So, if you go with gallons-per-100miles (call it gp100m), then the problem becomes a comparison as follows:
    What uses less gas:
    Going from 10 gp100m (10mpg) to 5 gp100m (20mpg)
    or
    Going from 3.03 gp100m (33mpg) to 2 gp100m (50mpg)
    Yes, for a comparative analysis as was presented, someone would now pick the former and not the latter But, if asked which is a better rate overall, they would instinctively pick 10 over the others as a good rate just because it is bigger. Maybe people could get used to the idea but I don't have much confidence in that.
     
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  68. I am not sure gpm is psychologically acceptable. Usually bigger is considered to be better (larger numbers). A gpm of zero would ideally be the best and as you "stomp on it" it heads to maximum (99 on my Jeep).
    So, if you go with gallons-per-100miles (call it gp100m), then the problem becomes a comparison as follows:
    What uses less gas:
    Going from 10 gp100m (10mpg) to 5 gp100m (20mpg)
    or
    Going from 3.03 gp100m (33mpg) to 2 gp100m (50mpg)
    Yes, for a comparative analysis as was presented, someone would now pick the former and not the latter But, if asked which is a better rate overall, they would instinctively pick 10 over the others as a good rate just because it is bigger. Maybe people could get used to the idea but I don't have much confidence in that.
     
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  69. The question of whether MPG or GPM is a better measure depends on which is the more "fixed"; the miles or the gallons.
    For most people, the miles they drive are fixed. They drive the same amount regardless of how much each gallon costs. In this situation GPM gives you better information.
    But if the gallons were fixed (for example if they were rationed and you only got 10 per week) MPG would give you better information. You'd want to know how far you could go on what you have.
    If gas prices rise very high the situation would become more like the rationing example above.
     
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  70. The point of the article is that government money would be more effectively spent if it was directed toward the first group of cars owners (the cars that get 10mph). Getting people to switch from 10mph cars to 20mph cars saves more gas as a nation than getting people to switch from 33mph to 50mph cars. If you were giving tax incentives to 1000 people of one of the two groups to switch there cars, giving to the first group would save more gas!!!
     
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  71. Quoted for truth:
    "People in the real world have to decide if it's smarter to replace their 10-year-old truck, or their 10-year-old Corolla. That's what this is about."
    Max really got it. Thank you.
     
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  72. Lol Americans fail. Just read the comments!
    I particuarly like the "Metric system uses arbitrary base numbers" comment #60, that's awesome.
    This article failed in 1 thing, and 1 thing only. Explaining WHY you care about the stated question, (10-20, or 33-50).
    And that is this, If you have the choice of upgrading cars. Your CityRunabout 33MPG car. OR your fuelpig 10mpg truck.
    For the sake of our argument, you go the same distance every week. 100 miles.
    Which car should you upgrade?
    CityRunabout (33mpg to 50mpg)
    OR
    FuelPig (10mpg to 20mpg)
    You do 100 miles per week in both cars.
    You can't afford to upgrade both cars. (real world)
    Don't apply this to a single car scenario, or you fail.
     
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  73. Excel to the Rescue. Lets say we use 15,000 Miles a year. 15,000M@10MPG@$3.00PG=$4,500.00 | 15,000M@20MPG@$3.00PG=$2,250.00 | 15,000M@33MPG@$3.00PG=$1,363.00| 15,000M@50MPG@$3.00PG=$900.00
    15,000M@100MPG@$3.00PG=$450.00
    15,000M@200MPG@$3.00PG=$225.00
    As you can see projected yearly saving might help the consumer make a more informed decision. Once we get past 50MPG getting to 100MPG will only save you $450 dollars a year. Now if that new 100MPG tech costs a $2000.00 premium it will take 4 years to break even and that's not counting depreciation.
     
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  74. Like "Stupid American" said, the math used in this article (and the original Duke article cited) is simply the inverse. MPG is the inverse of Gallons per mile, which is the same as liters per kilometer. Somehow these people at Duke came to a right answer with bad math. The ONLY way for a car getting 20mpg to be more efficient per 100 miles, etc., is when the car getting 20mpg has a larger tank than the one getting 50mpg. If all cars had a 20 gallon tank then this would be easier to see. If a Tahoe and an Altima have a 20 gal. tank and the Tahoe gets 20mpg and the Altima gets 25mpg (per 100 miles) you would see that the Tahoe is less efficient because it's using a gallon more per 100 miles (which in $$ is only $2.50, but it will add up). Otherwise, that math used is not accurate and misleading. Obviously using a system that tells us how many gallons we'll use per 100 miles is more effective than a system that tells us how many gallons we'll use per 1 mile (which would be the inverse already mentioned; liters per kilometer is still only measuring one unit-one kilometer. They're not measuring per 100km either). John, your audacity to say everyone ELSE uses bad math is saddening. Re-read the Duke article and see it.
     
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  75. Basically, the Government is where this matters.
    Example:
    Americans drive 1 billion miles and have 1 million cars. on average, 1000 miles per car.
    Given: the average doesn't change. (In reality, it will change a bit, but it is an average, stays roughly the same).
    There are 2 types of car on the roads.
    10mpg cars and 33mpg cars.
    50-50 distribution.
    Do you upgrade (or help people with subsidies) the 10mpg cars to 20mpg?
    OR
    promote upgrading the 33mpg cars to 50mpg?
    Which option will save more money/petrol.
     
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  76. One number is not inherently superior to the other, it just depends what information you have and what you want to get.
    I also think that people with 10mpg cars are aware of how much more they cost to run than a 33mpg car. That is because they are filling them up at a greater than 3x rate (see, that was an easy calc for mpg). Those are the people who are making the decisions, not the "think fast: abstract biased* calculation, go!" people.
    * you could come up with a complementary question that was easier with mpg than lp100km and "prove" that lp100km makes people ignorant.
     
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  77. Wow, based on the comments here I have to say that American's are both stubborn AND stupid. The number of comments here that suggest that it is indeed linear are only serving to emphasize what the study authors are saying: the American public has it wrong.
    The math presented here IS good. Obviously a 50 MPG car is more fuel efficient than a 10 MPG car. However, the point here is that there are diminishing returns on increasing fuel efficiency. Increasing your mileage from 10 MPG to 20 MPG decreases your fuel consumption by 50%, while increasing it from 33 MPG to 50 MPG only decreases it by 33%. If you own a 10 MPG car and a 33 MPG car and you have a choice to upgrade the 10 to a 20 or the 33 to a 50, you're better off upgrading the 10 MPG car (assuming they're both driven the same amount).
    This is exactly why the Cash For Clunkers program was focused on upgrading cars from mileage in the 10s to mileage in the 20s, rather than getting people to trade in their 20 MPG cars for 30 MPG models.
    P.S. How does the size of the fuel tank have anything at all to do with the mileage a car gets (as one poster suggested)?
     
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  78. Read all of the comments and here's why everyone's all in a huff- the article starts by explaining that upgrading a 10mpg to a 20mpg is a better saving than upgrading a 33mpg to a 50mpg, but then it switches to telling us why the metric system is better, which is irrelevant. Switching to the metric system doesn't change how much gas is in the tank (just the numbers we use to calculate it) nor how much gas that car uses. Metric is just a different system for measuring the same thing. The really big issue is that all these different, irrelevant points aren't relatable like readers are trying to make them. The author isn't trying to compare the 10 and 20mpg cars to the 33 and 55mpg cars- and he's not taking into account the fact that there aren't the groups that consumers are working in. A consumer will want to go from a 10 or 20mpg car to that 33 or 50mpg, not between the two groups he's described (I don't know anyone who is looking to buy a 20 year old, 10mpg car). He's mixed points and it's confusing people. Besides, most Americans buy their cars based on looks and not efficiency and that's probably not going to change.
     
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  79. I think Americans are misunderstanding the question and telling you that 50mpg is better than 20mpg! But mathematically they really can be quite dumb.. there are plenty of Youtube videos showing that quite clearly.
     
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  80. Well, this is truly a stupid article, especially since it doesnt even point out the simple mistake being made. Oh yeah that type of question is posed to every US student in the 8th grade or sooner. Its meant to be a "trick" question, so it doesn't surprise me that people make the wrong snap decision.
    10 MPG to 20 MPG = 100% increase in efficiency
    33 MPG to 50 MPG = 34% increase in efficiency
    It is really that simple, the rest of the world uses consumption per 100 KM/Miles - so essentially the rest of the world doesn't believe their populace can handle fractions, so they do it for you, fortunately for Americans we learn fractions at a very early age, so we don't require a company or government agency to do them for us.
    As for the Electric cars, America is very trendy and that is why the Prius does so well, it is normally driven by people who want to appear "green'. The truth of the matter is, the ecological damage caused by the production and disposal of a Prius far out weighs the ecological impact of a 1969 Camaro bug block being driven throughout its life span. Electric cars are not GREEN, they are not GOOD for the environment, if you want to feel good about yourself, plant a tree, or buy a VW Jetta Turbo Diesel, Honda civic Hybrid (no batteries, actually built with the best ecological impact in mind)
    Anyway, Troll on
     
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  81. @DandiGirl: The article *mentioned* the metric system, but it was talking about changing from MPG to GPM.
    It was talking about how countries with the Metric System use the better of the 2 numbers. (For ease of accurate comparison).
    the 2 numbers represent the same information. Comparing the 2 numbers is *easier* for a layperson in GPM.
    The informed person, or the person willing to do some maths *should* get the same amount of information out of both GPM and MPG. Sadly the "informed person" is an endangered species. The "willing to do some maths" person is critically endangered, if not extinct.
     
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  82. mpg gal per 100 mi
    10 10.0
    15 6.7
    20 5.0
    25 4.0
    30 3.3
    35 2.9
    40 2.5
    45 2.2
    50 2.0
    As you can see, a 5-mpg upgrade on a 10-mpg car saves a LOT more gallons of gas than a 5-mpg upgrade on a 20- or 30-mpg car. Conversely, going from 40 to 41 is peanuts compared to going from 10 to 11.
    The most important metric, at the end of the day, is gallons used. And we want to measure that relative to the benefit we get (miles traveled); so the most relevant metric is gallons per [N] mile(s).
    The 'gallons' measure really, really, REALLY needs to be on top. We're not used to looking at inverse measurements like mpg, and we chronically misunderstand them.
     
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  83. 10mpg car x 16 gal gas = 160 miles
    20mpg car x 16 gal gas = 320 miles
    33mpg car x 16 gal gas = 528 miles
    50mpg car x 16 gal gas = 800 miles
    For the ($3/gal) $48 we both just put in our cars, you made than 100 mile trip 3 times and I made it 8. You can have your "savings," Mr Math Wizard.
     
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  84. 10mpg car x 16 gal = 160 miles
    20mpg car x 16 gal = 320 miles
    33mpg car x 16 gal = 528 miles
    50mpg car x 16 gal = 800 miles
    For the ($3/gal) $48 we both just put in our cars, you made than 100 mile trip 3 times and I made it 8. You can have your "savings," Mr Math Wizard.
     
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  85. DandiGirl ... What's confusing is how you came up with your last statement. Did you read the full article? In it he says "Measure fuel usage the way the entire rest of the world (including Canada) does: consumption over distance. There, it's mostly liters per 100 km. Here, it'd be gallons per 100 miles."
    He's not saying use liters per 100km, he is saying use gallons per 100 miles. Honestly they should use bigger numbers like Gallons per 15,000 miles. For 15,000 miles going from a 10mpg to 20mpg saves 750 gallons! For that same 15,000 miles going from a 30mpg to 50mpg saves you 200 gallons a year. No question that going from a 10mpg to 50mpg will save 1200 gallons a year. But now I have a 50mpg car do we need to push for a 60mpg car? That will only save me 50 gallons a year. Or should I wait for the 90mpg car? An extra 40mpg saving has to make a big dent? Nope only an additional 134 gallons a year or $402 in savings.
     
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  86. Interesting article, and I actually did learn something. It seems many of the people leaving comments simply don't understand the math.
    Lets say I have a car that gets 10 mpg and gas costs $2.60 a gallon. I decide to replace it with a car that gets 20 mpg. Driving 10000 miles I pay $2600 for gas for the car that gets 10 mpg and I pay $1300 for the car that gets 20 mpg. I save $1300.
    Now lets say I have a car that gets 30 mpg and I replace it with a car that gets 50 mpg. Driving 10000 miles with the cost of gas at $2.60 I pay $866.67 in gas for the car that gets 30 mpg and $520 for the car that gets 50 mpg. I save $346.67.
    Increasing the mpg from 10 to 20 is a difference of 10 mpg. Increasing the mpg from 30 to 50 is a difference of 20 mpg. This is where I think many people have a problem. They think that there will be more savings going from 30 to 50 mpg than 10 to 20 mpg. Of course driving a car that gets 50 mpg is cheaper than one that gets 30 mpg, but that is not the point of the article. Do the math, it will always be right.
     
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  87. Wow this article is stupid. It assumes that people own both a 10 mpg car and a 33 mpg car and choose to upgrade one or the other... You upgrade the car you *own*, not your neighbor's SUV...
     
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  88. "A Stupid American"
    Yes, it would `just be the inverse.' However it'd be much easier--and far more intuitive--to compare the marginal difference in efficiency. The marginal difference is what matters most because individuals and society as a whole achieve more carbon savings per dollar (both literally for the vehicle, but similarly in social cost) by upgrading people from 10mpg to 20mpg than from 30mpg to 50mpg.
    It shouldn't be surprising that the notion of marginal cost versus absolute cost is not intuitive for most people, even learned people (because understanding and internalizing are different things). It seems obvious when carefully explained but the issue is at the root of such topics as communism versus capitalism and a host of other political-economic developments that have occurred in only the past few hundred years.
    Those who stoop to calling other people "stupid" for not understanding this almost certainly make the same errors elsewhere in their [economic] lives without realizing it.
    Changing the efficiency notation will systematically adjust for this inherent cognitive bias. In other words, it's one of those rare solutions that is cheap and easy to implement yet with significant returns.
     
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  89. ROFL - the only thing the author got wrong was "Americans aren't stupid." This comment thread is a total crackup.
    Apart from the few that got it, most of you have totally missed the point he was making and the rest served to prove his point that most don't understand how mpg actually relates to usage and savings.
    Hint, the question was; "Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg?" With the operative phrase being "which saves more gasoline"
    metric ftw!
    from Bob: 'The problem with the metric system is that its base units are completely arbitrary, and it divides poorly unless you are using the prime numbers 2 or 5. Compare the "English" system, which sticks to a base of 12 for most of its units, and thus can divide well by 2,3,4, and 6.'
    That arbitrary base that metric uses is 10. A very tricky and complicated system to deal with that requires proficiency in both the 2 AND 5 times tables. And judging by the comments here most likely too cognitively taxing for the average American and probably best left to the rest of the world.
     
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  90. Let me make it clear for the mentally challenged out there. You and your wife have one 10 mpg and one 33 mpg cars and drive to the same work every day. If you replace the 10 mpg car with 20 mpg car your family will save 5 times more gas than if you replaced the 33 mpg with 50 mpg. This is the whole point of the article and I am amazed how many people don't get it. What it means is that we should focus on replacing old clunkers first, rather than upgrading already decent mpg cars.
     
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  91. Wow, you Americans really need to rethink how and how much maths you teach in school/high-school. I would particularly recommend some study of the functions y=C*x and y=C'/x
     
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  92. wow... fail, it's just.. % increase. mpg is the best consumption number one can use. it's just the higher the efficiency gets, the harder it is to get that same % increase. math fail.
     
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  93. lol, senior editor so dumb xD
     
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  94. $2/gallon gas, that's the problem. Gasoline is more than twice as expensive in Europe.
     
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  95. Alright,
    While I get the point for comparissons, the fact is Miles per gallon is more PRACTICAL as it presents the solution in terms of the problem - how much gas do I need ? The problem is never 'how far can I go ?'- Ìf I'm going 35 miles and I have a 10 MPG car, I'm going to need 3.5 gallons.
    Thats it - simple math based on rate of consumption.
    The math is not more complicated with G/100 miles, but the problem needs to be reframed. Gallons per mile might make it simpler, but the number would be a small fraction which does make the math less simple (in a child like way).
     
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  96. Douches, if you don't like buying gas, then fucking walk.
     
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  97. I think the point of this article was simply the fact that if you have 2 vehicles. One being a work truck that gets 10 MPG and a car that gets 33 MPG and you wanted to upgrade one of them upgrading the work truck first, even if only to a 20 MPG version would be much "Greener" than upgrading the 33 MPG vehicle to the fashionable 50 MPG Prius. My take away from this article was "Do the math to make sure you're getting the best fuel economy possible, don't just believe the hype". Of course ultimately, everyone wants the highest MPG they can get at a reasonable price.
     
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  98. It's funny how the comments changed from "You are stoopid, get a life" to intelligent debate once Slashdot got involved.
     
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  99. @Tim:
    Re: high mileage 'European' cars. There are several reasons, but none have to do with the Europeans having some secret formula for high mpg.
    We use US gallons, they use imperial. 1 gal US = 1.2 gal Imperial, so right there is 20% more "mpg"
    Many of their cars are diesels which again gives the "mpg" a boost (even though diesel usually costs more)
    We generally drive long distances at high speeds - a trip across the US can take days of driving @ 70+ mph. England is roughly the size of Oregon, but with 60 million people crammed in. You can cross that in 1 day @ 55 mph.
    European are often missing safety features in place for US high speed crashes, the europeans save hundreds of pounds in weight.
    So buy yourself a car, strip out all the air bags, AC, side impact bars, etc....measure your fuel in imperial gallons and don't drive over 55mph and you too can experience this 'great' European gas mileage.
     
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  100. I would also suggest even 'gallons per mile' has short comings where various fuels are involved. Which is better 20mpg on E85 ethanol, 24mpg on gasoline or 26mpg on diesel? Well, around here, E85 is 1.89/gallon, gasoline is 2.45 and diesel is 2.70. So E85 = 9.45 cents/mile, gasoline = 10.2 cents/mile and diesel = 10.4 cents/mile. Getting 20mpg with the cheaper fuel is actually a savings over 26mpg with diesel!
     
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  101. I would also suggest even 'gallons per mile' has short comings where various fuels are involved. Which is better 20mpg on E85 ethanol, 24mpg on gasoline or 26mpg on diesel? Well, around here, E85 is 1.89/gallon, gasoline is 2.45 and diesel is 2.70. So E85 = 9.45 cents/mile, gasoline = 10.2 cents/mile and diesel = 10.4 cents/mile. Getting 20mpg with the cheaper fuel is actually a savings over 26mpg with diesel!
     
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  102. Gee! And I thought that I could just divide the distance by the MPG rate to find out how many gallons my car uses!?! Glad to be set straight! [And we believe the USA government schools provide a quality education?]
     
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  103. thank you.
     
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  104. @John: The only way to go would be the side-by-side option, as you mentioned. As you can see by the vitriol posted in response to your article, we are too stupid and stubborn to accept anything new. Sad.
    @narco: yeah, it's just too bad we're 15 months late.
    @DandiGirl: I've never seen a Slashdotter who went and posted on the article, and still didn't RTFA. Maybe you're really from Digg.
    @Aidan: John's point is that people don't realize that the percentage difference is how you calculate total improvement to their fuel consumption.
    @Kenz: Mine goes to 11. Just make the base 1000 miles rather than 100. Voila! Instant bigger numbers. Also, John's whole point is that going from 100 to 105 isn't really that big of a deal, which is much more obvious when you compare 2.35 with 2.24.
     
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  105. I think what they're saying is that consumers are opting to replace their 33 mpg sedan with a 50 mpg hybrid. They are then not giving a second thought to driving around their aging SUV. When what they should have done was kept the sedan and gotten a more fuel efficient SUV.
     
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  106. Distance per set volume is essentially identical to volume per set distance. They're entirely interchangeable.

    I'm Canadian, but to declare that the Americans are "ignorantly clinging" to their MPG method just serves to show that you don't have a grasp on basic units of measure.

    If anything, measuring your volume of fuel consumed over an arbitrarily assigned distance (100km) is more convoluted from a scientific standpoint.

    To go to this much effort to write a story about a logical approach to fuel economy... I would have expected you to mention that an approach such as Watts/m or kW/km would have been far more appropriate.
     
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  107. you must have been paid for this crap! I am glad that most of the comments I read can figure it out... so americans are not stupid after all. Now I am left wondering why you wrote this sh***t.
     
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  108. Did anyone even read the article?

    He is saying that if, in a family, they own a 10mpg vehicle AND a 33mpg vehicle, that it would save a lot more gas to replace the 10mpg with a 20mpg rather than the 33mpg with a 50mpg. Wow, you people (commenters) are the idiots. Reading comprehension goes a long way. I know this article is incredibly old, but I can't believe that someone logical didn't put these morons in their place back in 2009.

    Anyways, if the lower mpg vehicle gets replaced, it will save the "family" 5 gallons per 100 miles with the same 3 gallon use for 100 miles with the 33mpg vehicle. So for both vehicles it would use 8 gallons to move both cars 100miles.

    Now if it were the opposite, and the "family" replaced the 33mpg with...
     
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  109. ...the 50mpg car, then the savings are only of 1 gallon of gas. So to go 100 miles, the 50mpg takes 2 gallons and the 10mpg takes 10, which means that to move BOTH vehicles 100 miles it would use 12 gallons of gas. SO, the point of the article was that money would be saved on gas, buy upgrading low mileage vehicles, rather than keeping the low mileage vehicles and upgrading your already high(er) mileage vehicles.
    Dipshits! Wasn't that hard of a concept to grasp
     
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  110. The "moves toward putting consumption on window stickers" link is broken John. Otherwise another well done article though.
     
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  111. @Tom Thanks for the good words. That link was to a 2009 bill in the House of Representatives that's no longer live, so I just removed it.
     
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  112. I think L/100 Km is stupid. I wish they would change to Km/L here in Canada.
     
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