Diesel Cars: Six Important Things Everyone Should Know (But May Not)

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2013 Porsche Cayenne Diesel, 2012 New York Auto Show

2013 Porsche Cayenne Diesel, 2012 New York Auto Show

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It's an exciting time for diesel fans in the U.S, with automakers finally waking up to that section of the market that longs for great highway MPG and lots of torque.

Most people already know the benefits of modern diesels, but there are a few general things that people may have missed.

So in the spirit of eight important things you should know about electric cars, here are six important things you should know about diesels.

(1) They're at their most efficient on the highway

Hybrid cars and diesels are both known for fuel efficiency, but both go about it in very different ways.

If you've ever looked at the EPA stickers for each gas-saving vehicle, you'll have noticed that hybrids do particularly well in city driving, and diesels on the highway. That highway performance is because diesel vehicles develop plenty of power and torque at relatively low engine revolutions.

That means you can pair them with quite tall gearing. And that in turn means they not only sit at low, efficient revs at highway speeds, but there's generally enough power available that you aren't forever changing down when climbing hills, wasting even more fuel.

(2) Diesel fuel is pricier

In some countries, running a diesel is a no-brainer from an economic standpoint. In some European countries, and in places like India, diesel is cheaper than gasoline--so the financial benefits are huge.

That isn't the case in the U.S, for three key reasons--explained by the U.S. Energy Information Administration.

The first is demand. As a fuel oil with a greater spectrum of uses than gasoline, demand is high worldwide. Relatively low supply to demand keeps prices high. In vehicles, the lower-polluting, lower-sulfur diesels used in road transport are more expensive to produce, pushing up the price.

Finally, federal taxation on diesel is 24.4 cents per gallon--6 cents more than gasoline.

(3) The cars are pricier too

It isn't just the fuel that costs more--the cars are more expensive too. A Volkswagen Jetta TDI starts at $23,055, around four grand more than a 170-horsepower 2.5-liter gasoline Jetta, and only a few thousand less than the $24,995 hybrid model with its twin drivetrains and battery pack.

2013 Volkswagen Beetle TDI

2013 Volkswagen Beetle TDI

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Those differences are reflected across the board for diesel models. To meet tough emissions regulations, modern diesels are more complex than the average gasoline engine--with urea injection and other systems to clean up their tailpipes.

In an effort to improve driveability and refinement, dual-mass flywheels, particulate filters and extra sound-dampening also add to the vehicle's cost of manufacture. And that cost is passed down to you.

(4) Diesel smells...

This you might not know--or maybe it's the reason you still won't touch even the modern diesel cars, despite their improvements.

Unlike gasoline, which rapidly evaporates in air, diesel lingers for longer. It doesn't smell particularly pleasant and it's slick to the touch, which isn't great considering how many fuel pump handles seem to be covered in the stuff.

We just wish more U.S. stations would supply disposable gloves like their counterparts in Europe--it makes filling with diesel much more pleasant.

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Comments (23)
  1. Nice article. I learned some things.

    I didn't realize the federal tax on diesel was higher than on gasoline. I wonder why that is.

    Diesel smells. Hmmm never really thought about that aspect, but he is right. But I don't think I have ever seen disposable gloves at gas stations.

    Kinda of amazing that we accept a fuel dispensing system than routinely dribbles this toxic stuff.

  2. Gasoline stinks as well, and I don't really see the difference. Personalyl when I fill up I try not to get either on me and also try to stand upwind and not breathe the stuff.

  3. I think the difference is persistence. Gasoline, in an unenclosed space, evaporates very quickly. Diesel, not so much.

  4. Diesel has kind of a sweet smell to it. It doesn't vaporize either. Gasoline vaporizes. Those with hybrids who do not live in cities that regulate gas station emissions are polluting every time they fill up because the vapors displaced from the tank when filling up have no where else to go but into the air. Diesels don't have this issue. The diesel tax is another way to dip into EVERYBODY'S pocket because diesel trucks move everything. Thus, everybody (even environmentalists) pays when they buy their organic whatever.

  5. Not a very well done article. The difference in price is no where near $4000. The equipment level of the TDI is far higher than the gas model. The real difference is closer to $1600. The EPA ratings for the hybrid are very optimistic and the ratings for the diesel are very pessimistic and in the real world, the diesel easily exceeds the EPA ratings but very few people can equal the EPA ratings of the hybrid. Finding diesel fuel has never been a problem and I have never found the odour to be an issue.

  6. Diesel cars exceed EPA hwy rating easily, not necessarily so in the city.

    Hybrids on the other hand is opposite. They do well in the city, but less so on the hwy.

  7. I average 45 mpg city/highway in my Golf TDi. I spend more time in the city than the highway. Driving style determines mpg, not EPA ratings.

  8. Point taken, but you can't get a TDI with an equipment level equivalent to the base gasoline Jetta. So for the person who doesn't care about the bells and whistles, they're looking at a $4k difference.

  9. Do new diesel cars require urea? Is the urea expensive? My observation is that a base Jetta TDI carries a $10,000 premium over the base gas Jetta!

  10. We love our Jetta Wagon TDI and it was about $4000 more than the non diesel. We can carry lots of stuff and our kayaks too and maintain a 42-52 mile per gallon average city or highway; flat or mountainous.

  11. Urea is now available at O'Reilly and Pepboys for a serious discount from dealership costs.

  12. See my other post, the real difference in price is about $1600 and the Jetta does not use urea. The Passat does use urea but it is not a major cost ($16-$24 for 10,000 miles. Not sure where you have been shopping but the only way to get a $10,000 difference is to compare an absolutely stripped gas model with an absolutely loaded TDI. Not really the way to comparison shop.

  13. I've owned five VW diesels beginning with the mighty 1978 48 hp version. Since my daily commute is ~80 miles round trip the diesel pays for itself: I'm getting well over 50 mpg at my steady 62 mph on usually open roads. One factor you didn't mention is the higher resale value vs. the gas versions of my current Jetta Sportwagen. I've found, especially with the 21st Century TDI's I've owned that I get back, in higher residual value, the extra cost of the diesel engine. (As an aside, I always carry a supply of latex gloves for refueling...)

  14. I am definitely missing one of the most important differences of diesel in this list, which is that it has a much higher exhaust of soot (even with modern filters) and especially nitrogen oxides (NOx). About 20 times or so more NOx compared to gasoline engines. And that's responsible for a big amount of smog, asthma, cancer and other lung problems. Here's one of many articles that explain the huge health implications of diesel engines: http://www.drive.com.au/Editorial/ArticleDetail.aspx?ArticleID=40556&IsPgd=0

  15. Actually, diesels with filters have far fewer particle emissions than even the best gassers. Many studies have shown that particle emissions from diesel engines with DPF is essentially indistinguishable from HEPA-filtered background air, and even lower than background air in a few studies (e.g., http://www.dieselnet.com/papers/0209czerwinski/). Furthermore, a recent study has shown that exhaust from 2007-compliant diesel truck engines have essentially no health effects on lab test animals (http://pubs.healtheffects.org/getfile.php?u=708).

    Diesels may have marginally higher NOx emissions, but gassers have higher NMOG/VOC emissions, which are more responsible for ozone than NOx.

  16. I drive a 2007 camry Hybrid and I always do better than the EPA MPG. (between 36 and 48 MPG) I will also add that Toyota Hybrids do better on the Hwy than they do with city driving.

  17. That's been my experience as well. At 60mph my 2012 Prius averages 60+mpg. Even my 2005 Prius would be well into the 50s on the freeway. Most people have no problem hitting EPA in these cars. Still, diesels are a great option for some people so I'm happy to see efficient clean models available.

  18. The EPA ratings for a 2012 VW gas engine is .02gms/mile NOx and the diesel at .07gms/mile NOx. Not exactly 20 times!

  19. "To meet tough emissions regulations, modern diesels are more complex than the average gasoline engine--with urea injection and other systems to clean up their tailpipes."

    Incorrect! Have you actually spent any time *studying* the emission control systems in a modern diesel engine? Apparently not! The most "complex" part of the system is the recirculation valve, which is often mechanical, and the emission sensor, which is functionally equivalent to the O2 sensor. Oh, and let us not forget the "incredibly complex" extra injector for the self-cleaning diesel particulate filter.

    How many years automechanical experience did you write you had again?

  20. "let us not forget the "incredibly complex" extra injector for the self-cleaning diesel particulate filter"

    what does those particulates go? Oh, they "try" to burn it off by dumping fuel into the hot exhaust... Dodge's diesel truck does just that. When that happens, the MPG drops to the single digit.

  21. Fine particulates? In Oz, we are well behind Europe in our standards for filters, though I don't know how that actually affects the cars on our roads (ie, they are imported).

  22. I bought an Audi A3 diesel 3 months ago. The reasons for the purchase were the combination of mileage, range, design, function, power, acceleration and overall experience. In a nutshell, it's my wife car and she drives it about 100 miles per day. She loves the car and I'm happy.

    The A3 has delivered on all the criteria that we expected, averaging 40.9 miles per gal for the life of the car. The passing power and torque make the car fun to drive with the ability to accelerate out of potentially dangerous situations on the hazardous southeast 95 corridor. Decisions to buy cars are many times driven by previous experiences. Her previous car was an 1998 Audi A6. We did sacrifice a smoother ride for much better mileage.

  23. No mention of the particulates that are far higher for diesel than petroleum. A diesel with 100K under its belt is particularly foul especially under load up hills. Electric is the answer.

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