Miles-Per-Gallon Is Just Stupid. No, Really, It Is.
How Are Electric-Car Batteries Made? Photos From Nissan's New Plant
Making a battery for an electric car is more like assembling microelectronics than the kind of... Read More
- #4LEADERBOARD RANK
- 2897ARTICLES CONTRIBUTED
- 1949COMMENTS POSTED
Add to circle
Also See
-
2013 Toyota Prius V: Hybrid Wagon Ultimate Guide
-
2012 Toyota RAV4 EV: First Drive From Behind...
-
2012 Toyota Prius C: Detroit Auto Show Video
See more video »
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.
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.)
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]
+++++++++++
Follow GreenCarReports on Facebook and Twitter.
Related Articles
-
GM Becomes First Automaker To Sign Call For Action On Climate Change
-
Less Than Half Of Shoppers Will Pay More For Green Cars
-
Green Sound Insulation Inside Doors Quiets 2013 Ford Escape
-
When Did Cars Become The Yardstick For Measuring Pollution?
-
Greenpeace Says VW Is Europe's Least Green Automaker: Video
-
Follow Us
On Facebook
Most Popular This Week
More »
Tesla Model S Vs Chevy Volt: Owner Compares Electric Cars 
BMW CEO To Germans: Get Over Your Angst, Buy Electric Cars... 
Can Tesla Raise More Than $1 Billion On Soaring Stock Price? 
Diesel Cars: Six Important Things Everyone Should Know (But May... 
North Carolina Wants To Make It Illegal For Tesla To E-Mail... Find Green Cars
Photo Galleries
More from High Gear Media
- Follow Us
Have an opinion?
Tim Posted: 3/13/2009 3:30pm PDT
"What about that car that does 70mpg?"
I don't get it.
waste of time Posted: 3/13/2009 3:31pm PDT
"waste of time"
oh jeez Posted: 3/13/2009 3:34pm PDT
"shut up"
Me Posted: 3/13/2009 3:34pm PDT
"Rockstar"
Derek Posted: 3/13/2009 3:37pm PDT
"GREAT ARTICLE, IDIOT"
skot Posted: 3/13/2009 3:39pm PDT
"Go Back to 5th Grade."
skot Posted: 3/13/2009 3:40pm PDT
"Go Back to 5th Grade."
skot Posted: 3/13/2009 3:40pm PDT
"Go Back to 5th Grade."
tm Posted: 3/13/2009 3:41pm PDT
"Math literacy"
John Voelcker Posted: 3/13/2009 3:46pm PDT
"Actually, Tim ..."
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?
Your a Dumbass Posted: 3/13/2009 3:48pm PDT
"You are stupid"
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
american Posted: 3/13/2009 3:48pm PDT
"whats with your logic"
Lex Posted: 3/13/2009 3:48pm PDT
"What are you talking about"
spinedoc Posted: 3/13/2009 3:50pm PDT
"Really?"
So maybe making that drivers ed. class mandatory would be a better solution.
asdasdasd Posted: 3/13/2009 3:51pm PDT
"WoW"
David Posted: 3/13/2009 3:54pm PDT
"Miles per gallon vs consumption."
David Posted: 3/13/2009 3:56pm PDT
"Miles per gallon vs consumption."
D-man Posted: 3/13/2009 3:57pm PDT
"Americans arent stupid"
John Voelcker Posted: 3/13/2009 3:57pm PDT
"Actually, Tim ..."
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?
Tilmann Posted: 3/13/2009 3:58pm PDT
"?????"
Kenz Dale Posted: 3/13/2009 3:59pm PDT
"Balderdash"
Steven Posted: 3/13/2009 4:00pm PDT
"Market percentage of vehicles"
continued below:
drunko Posted: 3/13/2009 4:00pm PDT
"Mr."
And this article is just a pointless math trick.
Steven Posted: 3/13/2009 4:00pm PDT
"..continued"
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.
Kenz Dale Posted: 3/13/2009 4:01pm PDT
"Balderdash Pt.2."
practical Posted: 3/13/2009 4:02pm PDT
"More Math"
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.
John Voelcker Posted: 3/13/2009 4:14pm PDT
"so, Lex ..."
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.
A Stupid American Posted: 3/13/2009 4:29pm PDT
"Say What?"
jcwinnie Posted: 3/13/2009 4:33pm PDT
"Big Oil Propaganda"
Beeno Posted: 3/13/2009 6:15pm PDT
"Fool"
Kevin Posted: 3/14/2009 12:21am PDT
"Sir"
RC Posted: 3/14/2009 4:00am PDT
"Stranger that fiction"
john Posted: 3/14/2009 7:56am PDT
"Good points / Bad message"
Aidan Posted: 3/14/2009 11:51am PDT
"What an annoying article"
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!
owlafaye Posted: 3/14/2009 1:44pm PDT
"retired"
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.
owlafaye Posted: 3/14/2009 1:47pm PDT
"Editor-in-Chief?"
Lonnie247 Posted: 3/14/2009 7:19pm PDT
"Article-fail, Comments-not so much"
Potter Posted: 5/16/2009 2:16pm PDT
"Older vehicles that get the same mileage"
Jonathan Posted: 7/19/2009 7:28pm PDT
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.
Norm Posted: 9/4/2009 8:08pm PDT
Mike Posted: 12/4/2009 8:42am PST
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.
Canadian Posted: 1/28/2010 3:55pm PST
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.
Nybble41 Posted: 6/8/2010 3:06pm PDT
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.
Vijay Posted: 6/8/2010 3:55pm PDT
"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.
david bandel Posted: 6/8/2010 3:56pm PDT
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.
John S Posted: 6/8/2010 4:25pm PDT
Reading some of these comments... I'm not so sure.
PS: The article is correct.
Kyle Posted: 6/8/2010 4:36pm PDT
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 ;)
Adam Fuller Posted: 6/8/2010 4:39pm PDT
Rick Posted: 6/8/2010 4:41pm PDT
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:
Jesse Posted: 6/8/2010 4:41pm PDT
deceptive Posted: 6/8/2010 4:46pm PDT
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.
the cash tree! Posted: 6/8/2010 4:47pm PDT
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.)
deceptive Posted: 6/8/2010 4:51pm PDT
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?
Adam Posted: 6/8/2010 4:53pm PDT
better Posted: 6/8/2010 4:55pm PDT
i'll net $3 for each transaction.
Jack Rabbit Posted: 6/8/2010 4:56pm PDT
better Posted: 6/8/2010 5:01pm PDT
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.
rd Posted: 6/8/2010 5:05pm PDT
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.
Tom Posted: 6/8/2010 5:05pm PDT
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."
Bob Posted: 6/8/2010 5:08pm PDT
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.
maarten Posted: 6/8/2010 5:18pm PDT
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
Bob Posted: 6/8/2010 5:19pm PDT
KC Posted: 6/8/2010 5:21pm PDT
Tim Posted: 6/8/2010 5:22pm PDT
Max Posted: 6/8/2010 5:52pm PDT
Ronald Kollman Posted: 6/8/2010 6:01pm PDT
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.
Ronald Kollman Posted: 6/8/2010 6:02pm PDT
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.
Colin Posted: 6/8/2010 6:13pm PDT
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.
Ray Posted: 6/8/2010 6:21pm PDT
Mathias Posted: 6/8/2010 6:21pm PDT
"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.
PeterA Posted: 6/8/2010 6:28pm PDT
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.
Peter Posted: 6/8/2010 6:33pm PDT
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.
DandiGirl Posted: 6/8/2010 6:35pm PDT
PeterA Posted: 6/8/2010 6:38pm PDT
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.
eightball Posted: 6/8/2010 6:40pm PDT
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.
hipp5 Posted: 6/8/2010 7:33pm PDT
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)?
DandiGirl Posted: 6/8/2010 7:37pm PDT
Myles Posted: 6/8/2010 7:42pm PDT
my 2 cents Posted: 6/8/2010 7:55pm PDT
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
PeterA Posted: 6/8/2010 7:58pm PDT
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.
Ryan G. Posted: 6/8/2010 8:15pm PDT
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.
MSquared Posted: 6/8/2010 8:22pm PDT
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.
MSquared Posted: 6/8/2010 8:22pm PDT
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.
Peter Posted: 6/8/2010 8:24pm PDT
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.
Mark Posted: 6/8/2010 8:36pm PDT
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.
David Posted: 6/8/2010 9:17pm PDT
Bill Posted: 6/8/2010 9:31pm PDT
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.
notaseppo Posted: 6/8/2010 9:35pm PDT
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.
ignorant Posted: 6/8/2010 10:58pm PDT
amazing Posted: 6/8/2010 11:45pm PDT
Sonny Posted: 6/9/2010 1:34am PDT
europena Posted: 6/9/2010 1:40am PDT
alain Posted: 6/9/2010 3:35am PDT
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).
John Holmes Posted: 6/9/2010 5:00am PDT
narco Posted: 6/9/2010 5:31am PDT
Corey Posted: 6/9/2010 6:22am PDT
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.
Corey Posted: 6/9/2010 6:29am PDT
Corey Posted: 6/9/2010 6:30am PDT
hikw Posted: 6/9/2010 6:51am PDT
orgelspieler Posted: 6/9/2010 6:59am PDT
@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.
Norbster Posted: 6/9/2010 7:04am PDT
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.
Have an opinion?Join the conversation!