• Oct 19th 2009 at 11:52AM
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2010 Volkswagen Golf TDI – Click above for high-res image gallery

The question is often asked, "Why is it that drivers in Europe can get all of these amazing high-mileage cars that get 50, 60 or even 70 mpg but we have to celebrate when we get half of that?" There are plenty of reasons, but one of the main ones is the remarkable compression ignition engine, more commonly known by the name of its inventor, the diesel.

In recent years, diesel engined vehicles have accounted for over half of all new vehicle sales in Europe – in some places like France and Italy, up to 80 percent. Yet here in the United States, these high-efficiency wonders represent a tiny minority of car sales. Only in the heavy duty truck segment do diesels grab any significant attention. Read on after the jump to learn why so few diesel cars are available in the U.S.

Photos copyright ©2009 Sam Abuelsamid / Weblogs, Inc.

There are a number of reasons for limited diesel availability in the U.S. but the two primary hurdles are cost and emissions regulations. Diesel engines are inherently more expensive to build than spark ignition engines that run on gasoline or ethanol. Because of the way a diesel functions, the engine components need to be more robust to withstand the high internal pressures. However, the implementation of much tighter emissions standards has exacerbated the cost problem significantly.

The current U.S. emissions standards fall under what is known as Tier 2 and were phased in between 2004 and 2009. There are currently 8 bins, or categories, that new light duty vehicles can certified for, with bin 1 being zero emissions. California standards are even tighter and for a vehicle to be allowed to go on sale there it must meet the equivalent of at least the national bin 5 standard. Thus Tier 2 bin 5 (T2B5) is the de facto minimum for any automaker that wants to sell a car nationwide.

Here is where the problem lies. T2B5 has significantly tighter requirements than older EU4 European standards when it comes to particulate and nitrogen oxide emissions. The particulate or "soot" emissions are the black clouds that we're all used to seeing pour out of the exhaust of big trucks as they accelerate down the road. This problem has been largely addressed by the use of diesel particulate filters (DPF) in exhaust.

The particulate filter uses a ceramic core to trap the particles that make up the smoke. Pressure sensors on the inlet and exhaust sides of the filter are used to detect when it is full at which point regeneration takes place. To regenerate the filter, the air/fuel mix in the engine is adjusted to temporarily raise the exhaust gas temperature above 600 C, which causes the soot to burn off.

DPFs have been increasingly common installations in Europe over the last several years as the EU5 standard has gone into effect with a limit slightly lower than the T2B5 standard.
The big difference is the NOx emissions. The EU5 standards dropped the limit from .25 g/km to .18 g/km. T2B5 slashes that to only .04 g/km. Even the 2013 EU6 standard brings the standard to only .08 g/km. Eliminating NOx is not easy. Nitrogen oxides are produced when the temperature of combustion gets above about 1600°C. Modern common rail injection systems that allow for multiple fuel injection pulses along with exhaust gas recirculation have helped to reduce combustion temperatures, thus cutting NOx production.

However, that is not enough to meet T2B5 requirements. For that we still need some additional exhaust after-treatment. Depending on the size of the vehicle, this can come in the form of either a lean NOx trap or urea injection (selective catalytic reduction). For the larger vehicles that are more common in the U.S., the urea injection systems are often the only way to go. This requires adding a storage tank for the urea solution that typically holds 4-8 gallons.

Depending on who you ask, the incremental cost of a Tier 2 Bin 5 compliant diesel over a similarly powerful gasoline engine can be $2,000 to $5,000. That's a hefty premium to overcome, especially when fuel prices are hovering at $2.50-2.75 a gallon. While a number of automakers including Honda, Kia and Nissan had indicated or announced outright they would introduce diesels to the U.S. market in 2009-10, all but VW, Mercedes and BMW have canceled or indefinitely suspended those plans.

Since mid-2008, when diesel prices spiked as much $1 a gallon more than gas followed by the economic collapse, all those automakers claimed that diesel just didn't economic sense here. Poor overall sales and the cost of certifying a new, low-volume powertrain mean that those looking for an affordable diesel are pretty much stuck with Volkswagen. So, the U.S. can get diesel cars, just not very many of them.

Thanks to David M. for the question.

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    • 1 Second Ago
      • 5 Years Ago
      What happens to the Nox and CO2 numbers when bio-diesel is used in place of petro-diesel?
      • 5 Years Ago
      I may be wrong, but I understand that from each barrel of crude oil, you can readily produce 1/3 barrel of gasoline and 1/3 barrel of diesel fuel. That means, given a limited supply of crude oil, something like half the folks need to be burning gasoline and half need to burn diesel. We, in the USA, are just the folks that get to burn the gasoline half.

      Building on that assumption, I don't really think environmental concerns or engine cost had that big an influence on what's going on. These arguments are just being used to placate American consumers that are frustrated they got stuck with the less efficient Otto cycle while the Europeans are taking advantage of the more efficient Diesel cycle.
      • 5 Years Ago
      Diesels just don't make a ton of sense in the smallest cars. The Diesel option is gone from the Aygo now. Fifth Gear tested a small Suzuki (and not like their Cooper test) with a gas and Diesel engine and the gas engine was more economical.

      In the end, you're going to pay a lot more for a Diesel engine and with the fuel economy these cars get (gas or Diesel), it's gonna be tough to get it that money back.

      Also, on this article: T2B5 is also tighter than the current Euro V Diesel standards for NOx, which means urea injection is here to stay for now.

      Also, if you make cars outside T2B5, you start to run into problems with fleet average calculations, as your fleet must average T2B5 outside the CARB area (it must average below T2B5 inside CARB). As you mention, this along with many other factors contributes to T2B5 being the highest bin any vehicle is offered in right now in the US.
      • 5 Years Ago
      In my opinion Bin 5 standards are way to conservative, and EPA is continuosly sabotaging Diesel efficiency technology availability. Green Gases are only spoken about - they mean nothing. Americans must burn the gasoline - fuel of American presence and future, shame...
      • 5 Years Ago
      Great article, why isn't Audi in the list along with BMW, MB and VW tho? Aren't they selling their Q-series with diesels?
      • 5 Years Ago
      You didn't bother to mention that a 50, 60, or 70mpg european diesel isn't really a 50, 60, or 70mpg diesel when it comes to the US. Due to the differences in cycles, it'll be rated more like 44, 52, or 61mpg. And have CO2 emissions more like a 38, 45, or 53mpg gasoline car, respectively.

      Also, while the majorly eco-minded crowd is willing to accept the very slow accel times that the super-efficient diesels carry (like much of Europe is), the average US buyer isn't. So they usually up the power, which in turn drops that mpg rating further.

      That said, we do deserve to have more selection in this market, so one can hope there will start being some more varied offerings in the US.
        • 5 Years Ago

        Good point on the CO2. Diesel contains more carbon per gallon and more carbon per BTU of energy.

        For example, Jetta Diesel tests for 63 mpg in the UK highway test gets tests at 41 mpg here.

        Its US carbon footprint of 6.2 tons CO2/year works out to be worse than a lot of regular gasoline vehicles in the same class, much less a Prius at 3.7.
        • 5 Years Ago
        Here on ABG we always quote mileage numbers in miles per US gallon regardless of how the test was done. We also try to mention the relevant test cycle. For example the EU or Japanese 10-15 cycle which is far more unrealistic than the Euro cycle.

        Given that, cars like the Smart ForTwo CDi is rated at 71 mpg (US) and the Fiesta ecoNetic is above 60 mpg (US)

        As for the Jetta, that 63 mpg in imperial gallons which equates to 52 mpg (US). While that is well above the EPA 2009 rating of 41 mpg (up to 42 mpg for 2010), it is not uncommon to get 50+mpg on the highway in the real world with a Jetta.

        The EU cycle may overestimate mileage, but real world experience indicates that the EPA underestimates diesel mileage by 10-15% or more.

        As for CO2, diesel fuel does contain more carbon than gasoline, (about 15%) but diesel engines are on average 30% more efficient than a similarly powerful gas engine and thus emit about 25% less CO2.
        • 5 Years Ago
        My personal opinion, not to be confused with facts:

        The reason the NOx numbers are set so low in California is that the government in that state does not like photochemical smog looming in what would otherwise be a beautiful place. "Photochemical smog is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere." It is bad for the health of the residents, but it's worse for economic development of cities. The end.

        Oh, and meme. Youyou need to lay off bashing Sam's comment. Picking apart someone's comment line by line makes your rebuttal seem childish, like your feelings were hurt or something. As for the "real world" consumption figures, I actually agree with Sam, government agencies ESTIMATE fuel consumption based on a short series of standard tests. Those tests do not account for feedback from the vehicle (throttle response, engine noises, etc.) that contribute to real driver input. That is, what is achieved in a standard test is not necessarily what is achieved by the average owner of a particular model.

        I propose that all of the current government test cycles be scrapped. What we need instead is a range of fuel consumption. We need consumption at an average highway speed to show aerodynamic and drive train efficiency, and we need a 0-60-0 test for consumption at a reasonable acceleration combined with any regenerative capabilities. THEN, we need a maximum efficiency number at a low highway speed (maybe 45 mph) and a minimum efficiency at a high interstate speed (maybe 80 mph). Do something similar with the accel/decel test (full throttle and full brake, then very light throttle and very light brake). What you'd end up with is two simple graphs showing max, min, and average fuel economy. Dumb people will still be able to look at the average numbers and choose without additional thought. People who know their driving habits will be able to discern which car is better for them based on their own driving style and commute. I don't see this creating a lot of extra work for the EPA or other agency since the testing cycles we currently have are much more complicated. I'll bet they have most of these numbers already, why not publish them somewhere?
        • 5 Years Ago
        This may not be entirely relevant to your point, Ray, but cars sold in different regions of the world are never exactly the *same car*. I'm not referring to which side the steering wheel is on, either. There would be no reason not to optimize performance for a regions given climate, driver types, etc, and I can tell you first hand that manufacturers definitely do this.

        Regarding the topic (which is getting a little overdone at this point, no offense to the author), the question(s) I would like to see answered is:

        Why is T2B5 just out of reach of what can be done without aftertreatment? Is that incremental difference in emissions significant to the environment in the case of small passenger cars?
        • 5 Years Ago
        "Here on ABG we always quote mileage numbers in miles per US gallon regardless of how the test was done."

        That's a straw man; I never raised the issue of US gallons vs. imperial gallons. I raised the issue of different drivecycles.

        And yes, the 10-15 cycle is even worse than the NEDC, but the NEDC is still worse than FTP-75/US06

        "As for the Jetta, that 63 mpg in imperial gallons which equates to 52 mpg (US). While that is well above the EPA 2009 rating of 41 mpg (up to 42 mpg for 2010)"

        Which is exactly what I said, only worse. I suggested 50mpg "US" NEDC = 44mpg "US" EPA. The actual, in this case, is 52 mpg "US" NEDC = 42 mpg "US" EPA.

        Given that you apparently *know* that NEDC numbers are higher than our numbers over here, why didn't you bother to mention that in your article on why we can't get cars with these extremely high mileages over here?

        ", it is not uncommon to get 50+mpg on the highway in the real world with a Jetta."

        Sorry, but we use drivecycles for a reason: to eliminate the differences in personal driving habits. Now, if you think you have discovered a *reason* for systemic bias in the FTP-75 and US06 drivecycle, submit it to the EPA, and if it passes review, *then* I'll care about your anecdotal claim. As it stands, I'd be willing to put money on you seeing heavy selection bias.

        "As for CO2, diesel fuel does contain more carbon than gasoline, (about 15%) but diesel engines are on average 30% more efficient than a similarly powerful gas engine and thus emit about 25% less CO2."

        Irrelevant. That's already factored into the mpg numbers. The CO2 difference is not, so it still needs to be canceled out. The greater efficiency of diesels is why they get better numbers than non-hybrid gasoline vehicles even after the CO2 difference is factored into account. It doesn't excuse the fact that you still need the CO2 difference factored into account.
        • 5 Years Ago

        californaria closed the well, after the cow fell in to it.

        it's rediculous the united states didn't raised taxes on gasoline a decado ago, like they did in the netherlands, a mere 25 cents on top on the next day.

        why does the US permit use carburators?
        germany doubled the circulation tax on all cars who don't have a catalitic converter more than 20 years ago.
        the problem would have solved it self a long time ago.

        why do the american think always their system is superior over the european system?
        witch is roughly 13x older than new york.

        germany has the TUV
        witch the world's most advanced Technical Inspection Association.
        i'm sure about 80% of all people on the world have seen their logo on somekind of comsumer product.
        witch is an INDEPENDENT consultant.

        than you have the ADAC, the drivers club, with is also the worlds most advanced Association in their territory.

        both test same cars, how can both associations be so wrong according to americans?

        the world biggest exporter.
        yes, they sell more then you with 305 million habitants.

        how can the rules be so strict if the domestic builders mostly offer v6 in their models?
        i live in a city with close to 800.000 habitants and about 80% or maby more is HDI/TDI/etc engined. i can't say if i realy smell the cars.

        don't act like the world's police officer, trying to be the example, meanwhile avoiding the koyoto act, because you don't like the develping economy's have less stricter of rthe present time.
        in other words you're still somewhat a develping economy?

        when i had my 90ps tdi mkIV golf, 10 years ago, i payed attention when i had a long road trip.
        volkswagen's statement was correct, 1000km on 50 liter diesel.
        i never fill up my tank, i always use 1 10 euro bills.
        i could travel significantly more than my previous 1600/2000 cc gasoline cars.
        ok, a litle less topspeed, but nevertheless sporty rapid in city traffic.
        witch is no doubly way more agressive than yours.

        p.s. i'm trying to have a neutral view on things, i'm not with you nor against you.
        i just say thing as it is.

      • 5 Years Ago
      Have 2 diesel cars - would NEVER cchanged them unless . . . I have to . . .
      1. 2008 MB GL320 CDI - with 3/4 of one tank I can drive from ATL to Miami with average speed of 70 mp/h.
      2. 2009 Jetta SW TDI - can not go below 38 mp/g in combined cycle. I drive almost 400 miles for less than 25$.

      here are my 5 cents related to this topic.

      1. In the past, diesel fuel has been more expensive in USA compared to gas since it was "dirty" fuels . A surcharge was given for every gallon of diesel that made diesel ultimately far more expensive that regular gas. Today with new diesel fuel in USA, part of those added "surcharges" have been removed (not entirely) . . . that made diesel more cheaper. Also, do not forget that in the past every car company (MB for instance) had to pay penalty for every diesel car that was sold in USA (early 90's) since technology was not clean. that is the MAIN reason companies did not want to have vehicles in USA nor even market the same.
      2. EVERY European government is subsidising diesel fuel. . . hence price of diesel is below of the price for regular gas. They also have "blue" diesel that is primary used for fishing . . . many many people have diesel cars simply to run it on that fuel. That "blue" diesel is subsidized even more that regular diesel . . . it comes almost to half the price of regular diesel.
      3. Diesel engine due its excesive weight is much more costly to put in "regular" car body since chassis has to be strengthent additionally. That creates hughe costs for manufactures. Take VW and its Routan. 3.0 TDI . . . it would make that engine ideal for Routan, it is almost idealistic that VW will allow that engine in that car. Why? VW is not contolling the costs of such improved and strengthend vehicle and number of those cars sold in USA are good appealing enough to take the risk
      4. Comparing the hybrid and diesel vehicle is not always "fair" task since you would have to agree about comparision merrits. Would you compare those two for a true cost to ownership. Would you consider battery replacement after 5-7 years with Prius. If someone is not willing to keep car that long . . . he/she/they do not care. But the one who buys the car does as costs to replace battery pack @ PRius I is 5-7k$. Added that to price of the vehicle and you will see that diesel is more appealing.
      5. Audi is selling Q7 and A3 . . . apparently they will come with A4 and A6 diesel. The issue Audi has is more on image side. They do not want to loose image of being the most appealing premium German car brand . . . diesel engine in their vehicle is not supporting that goal (as per Audi insider). MB is known for diesel so expect E-class to come as 350 Bluetec and 250/220 Bluetec.
      6. Toyota used to have the very best diesel engine in Europe (few years back) but bringing it to USA woudl kill Prius. That act would be widely recognize as "killing the hybrid" rather then support (as per Toytota).

      • 5 Years Ago
      "The big difference is the NOx emissions. The EU5 standards dropped the limit from .25 g/km to .18 g/km. T2B5 slashes that to only .04 g/km. Even the 2013 EU6 standard brings the standard to only .08 g/km. Eliminating NOx is not easy"

      I guess it is a pick your poison scenario. The pollution you can see, smell, and taste vs. CO2.

      Shouldn't the argument be more about why does Europe have such lacks NOx standards?

      I dont think anyone pushing for a cleaner environment can honestly support Diesel in its less clean form from Europe. From a conservation of resources standpoint it makes sense, but there is a trade off.
        • 5 Years Ago
        I know the German government is bringing in NOX standards, and will request all diesels be fitted with a filter. Better late then never.
        • 5 Years Ago
        As you pointed out diesels put out different poisons than gasoline engines, even the most efficient gasolines engines point out serious amounts of poisons. A 2.0 gas engine puts out 200% more Carbon Monxoide than the 2.0 diesel engine. Not to mention that if you have the same Hp count in either car the diesel will put out less Co2 and the particulate, soot count will be very similar. (within 5-10%) The hydrocarbon output in the diesel will be higher by a significant margin.

        In the end you just need to pick your poison and live with it.
      • 5 Years Ago
      One key reason missing for Europe is subsidized diesel gas. Many countries in Europe had lower taxes on diesel which makes diesel fuel cheaper than regular (now difference is smaller in most countries). While in the US diesel is actually in most places more expensive.

      Second I think % are mixed up with transport sales. Currently it's 80% on average for transport vehicles. I do not believe 80% of France sales are diesel. In Germany it's 28% and with their recent cash for clunkers that number dropped little bit.
      • 5 Years Ago
      Good article.

      Maybe it should be followed by "Why Can't Americans have fun to drive hybrids?" or "Why Americans who like cars and driving will continue to buy gasoline internal combustion engine cars".

      Saw an actual Tesla this weekend by the front door in the parking lot at Whole Foods. Lovely car. Ironic though. It drew no interest at all from that organic crowd. Smaller than I thought it would be.
        • 5 Years Ago
        One thing missing in all this: many people buy their cars to last over five years. I still drive a '97 Volvo. So the dilemma is "Should I buy a fossil fueled car now or wait for the BEVs that offer the promise of less complexity, less maintenance cost, less fuel cost, etc? You see all the news is about the gloom and doom of running gasoline and diesel cars and the outlook for returning to cheap oil is bleak; so...would one who keeps cars over 10 plus years take a chance on buying an obsolete diesel/gasoline driven car or opt to wait on the electric cars?....I'll wait thank you!
        • 5 Years Ago
        I think your post and mine are speaking in the affirmative for electric cars; but, I'm not sure because of your negative remark which adds nothing to you facts or point.
        • 5 Years Ago

        The tesla roadster has 8 moving parts in it

        It has a battery pack in it which has 6,831 battery cells which are hooked up to a computer management system which tells you specifically when a cell goes out

        The battery system has a temperature/ charging management system which heats and cools the battery and makes sure that it doesn't get over charged or over drained.

        That battery pack hooks up to an AC inverter which then pushes the electicity to a 3-phase, 4-pole electric motor pushing 248 hp and 200lb ft of torque (At 0 rpm all the way up to 6000 rpm)

        The Tesla roadster has a single gear, no clutch and no shifting

        The Tesla roadster is probably the most complex electric vehicle you can buy and i just built it for you in this post. Could you do that with an ICE car. Doubt it. What the hell are you smoking... Psh more complex...

        P.S. Woops i forgot the washer fluid...
        • 5 Years Ago
        @ lad

        wow... its a monday. sorry.
      • 5 Years Ago
      Small, efficient diesels would revolutionize the American automobile industry. First, diesels are much more efficient than a comparable gasoline engine. Second, with proper after treatment of the exhaust, they become as clean as any modern gas engine. Finally, the consumer would not notice any difference in power and drivability. One step further than a diesel only drivetrain is the diesel-electric hybrid drivetrain which enables the engine to run at maximum efficiency. Check out www.green-garage.org to see how several schools around the nation are attempting to create a truly economical vehicle.
      • 5 Years Ago
      Americans want their 5000 calorie McDonalds meal and a model body with no exercise too. you can't get that. The major reason Europeans get so much better mileage is the way they drive. They don't expect a car to go 0-60 in 8 seconds. They are happy with 12 seconds. The people i've talked to looked at me as if i was insane when i told them how fast people wanted their cars to go. Look at the average 0-60 times of average American cars up to the '80's and we didn't need 7-8 second cars. Only sports cars did those numbers. In 1981 an Audi 5000S did 0-60 in 11.6 seconds,1986 Buick Electra T Type 12.5,1983 Chevrolet Cavalier 13.1, 1976 Chevrolet Caprice Classic 400ci 12.8, 1974 Chevrolet Chevelle 400ci 11.4, 1992 Ford Crown Victoria LX 9.5, 1973 Ford LTD Brougham 429ci 10.4, 1973 Ford Pinto 13.7, you get the point. these numbers are from Road and Track, Motor Trend and Car and Driver.
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