A Diesel for Mr. Clean

In separate announcements, both Ricardo, a European automotive engineering firm, and Nissan recently announced that they are developing diesel engines that meet emissions standards that match the Toyota Prius. Does this mean that diesel vehicles are finally worthy of the "clean diesel" label?

Not quite yet, but apparently the time is coming closer. Neither company is saying when—or even if—Super Ultra Low Emission Vehicle (SULEV) diesels will enter production. California’s SULEV standard is an impressive goal, but the more immediate goal is for diesels to meet federal Tier 2, Bin 5 standard (T2B5).

Today, there is one diesel car and five diesel SUVs sold in the United States that meet the EPA’s less stringent Tier 2 Bin 8 (T2B8) emissions requirement. That means today’s diesels are still dirty enough to outlaw their sale in five states.

2007 Diesel Vehicles(sold in 45 states)

Mercedes-Benz E320 Bluetec
Mercedes-Benz R320 CDI 4matic
Mercedes-Benz ML320 CDI 4matic
Mercedes-Benz GL320 CDI 4matic
Jeep Grand Cherokee CRD
Volkswagen Touareg TDI

You’ll have to wait another year for cleaner diesel cars that meet Tier 2, Bin 5 (T2B5) standards. These models will be available for sale anywhere in the U.S.

2008 Diesel Vehicles – Announced (sold in 50 states)

Audi Q7 3.0 TDI
BMW 535d
Mercedes-Benz E320 Bluetec
Mercedes-Benz E320 Bluetec
Mercedes-Benz R320 CDI 4matic
Mercedes-Benz ML320 CDI 4matic
Mercedes-Benz GL320 CDI 4matic
Volkswagen Jetta TDI

Until the uncertain date when technology from Ricardo, Nissan, and others produce a diesel worthy of Mr. Clean, the T2B5 diesels will remain dirtier than the typical hybrid. The big issue is oxides of nitrogen (NOX)—gases which contribute to the formation of smog, particularly in cities. A T2B5 diesel in Los Angeles can emit as much NOX as three and-a-half Priuses. So while the new diesels are fuel efficient, they still pollute more, making them an environmental mixed bag.


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  • Jerry

    They match Hybrids!?! Are they factoring the engine shut down feature of the hybrid. Or just at speed. Sounds like GM type spin.

  • Bill

    Diesels are the noisy. You can’t even go for a walk in Europe anymore in a big city because of the diesel noise.

  • domboy

    I don’t suppose you’ve ever heard that these dirty diesels emmit a LOT less co2 than your sqeaky clean hybrids. Some of the new BMW models do shutdown the engine at stop. And as for noise, I happen to really like the bit of engine noise my little VW diesel makes. It’s got a lot of personality, instead of being a bland boring appliance car.

  • rocknerd

    It all depends on perspective. There is no need for the snotty attitude domboy.

    These engines are a step in the right direction. But one issue bothers me about diesel fuel efficiency:

    From the Union of Concerned Scientists-
    “The improved efficiency of diesel engines can also help reduce oil consumption. It should be noted, however, that it takes about 25% more oil to make a gallon of diesel fuel than a gallon of gasoline, so we should really look at how a vehicle does on fuel efficiency in terms of “oil equivalents.” Thus, we need to adjust the mileage claims for diesel vehicles downward by about 20% when comparing them to gasoline-powered vehicles.”

    So a diesel would have to get 62.5 mpg to match a 50 mpg Prius in terms of oil consumption.

    If we could make diesel from cellulose (not corn) then diesels win hands down. A diesel hybrid that runs on cellulose derived fuel would make me giddy as a schoolgirl. Now that’s a car with “personality”.

  • wxman

    One thing that should be taken into consideration is that diesel fuel is essentially non-volatile, unlike gasoline. Evaporative emissions from the production, distribution, refueling, and storage of gasoline are in addition to direct emissions from the vehicle itself.

    That means, in my opinion, that a SULEV diesel vehicle would actually be “cleaner” than a SULEV gasoline vehicle (or even an AT-PZEV vehicles for that matter).

  • rocknerd

    Wow, I’ve never considered the volatility of the fuels. It just goes to show that any combustion-based energy is really about chosing the lesser of many evils.

  • domboy

    Sorry if I came across as snotty. I just get tired of unfounded or ignorant comments on technology. I also get tired of exclusive attitudes. Hybrids aren’t the only efficient vehicles, and they also don’t appeal to everyone. Clean diesel is an alternative that could appeal to the car buyer that doesn’t want a hybrid. More options are always better, so don’t diss them. That’s all I’m trying to say.

  • DaveM

    I would expect the use of biological material for diesel and the development of clean diesel and diesel hybrid technologies could go a long way to switch the US from a mostly gas driving automative community to a broader mix.

    One of these days someone will figure out diesel hybrid with biofuels can be the best of both worlds.

  • Denis

    In response to rocknerd, i am not so sure whether it takes 25% more oil to produce a gallon of diesel then gasoline, with the refinery engineers that i work with, but lets say it does, the energy content of diesel makes up for it with almost double the gas mileage of an equivalent gasoline engine, that is still +25% gain. As well diesel is much easier and cheaper to produce then gasoline.

  • wxman

    Taking the evaporative emissions issue a step further, according to the EPA’s AP-42, there approximately 9.6 pounds of evaporative emissions for every 1000 gallons of gasoline throughput from the loading and transportation of gasoline to a gas station, and from the off loading and storage of the gasoline at the gas station. That’s assuming the latest and greatest in emission controls (Stage 1 vapor recovery, etc.).

    According to the EIA, currently about 385 million gallons of gasoline are consumed in the U.S. each day. 385,000,000 gallons X 365 days/year = over 140.5 billion gallons/year. That means that about 672,000 TONS of evaporative VOC emissions occur from these stages of gasoline “handling” each year.

    Also, according to AP-42, only about 0.0464 pounds of evaporative emissions per 1000 gallons come from the same stages of diesel fuel “handling”. So if hypothetically the entire light-duty fleet in the U.S. were switched over to diesel, using the same 140.5 billion gallons (which would be extreme since diesel vehicles typically use 25% – 30% less fuel per unit distance traveled) would yield about 3260 tons (i.e., less than 0.5% of the gasoline VOC emissions).

    Not only are VOCs important pollutants (contribute to ground-level ozone production (smog) and secondary organic particulate matter), 672,000 tons of product are simply wasted each year.

    Of course, this is hypothetical, since you’d still have gasoline even if you optimize a refinery to produce middle distillate (e.g., diesel fuel). However, a greater market share of diesel vehicles in the U.S. would help this issue proportionately. This is something the Sierra Clubs and UCSs should consider before they bash light-duty diesel penetration in the U.S., in my opinion.

  • rocknerd

    I was just quoting numbers that I have read. I am no petroleum engineer. The numbers are backed up by our very own Department of Energy though.

    “with almost double the gas mileage of an equivalent gasoline engine”. My corolla gets 38 mpg. Are there really diesels out there that get 70-80 mpg? I think you need to compare truely equivalent engines.

    On another note – No worries Domboy, I’m snotty sometimes too.

  • rocknerd

    how is calculating the effieciency of vehicles using common units (in this case “oil equivalents”) considered “bashing”? I think this is a step in the right direction toward a wholistic energy perspective.

    That sounds like hippie bulls**t but in this case it is true.

  • wxman

    rocknerd – I was actually referring to vehicle emissions (direct and indirect). The “environmentalists” continue to oppose light-duty diesels based on “smog-forming” NOx emissions and “cancer-causing” PM emissions, without mentioning their lower “smog-forming” hydrocarbon/VOC emissions and “acutely toxic” CO emissions.

    Actually now that you mention it, UCS in their “The Diesel Dilemma” report (I’m not sure if this is the source of your “oil equivalents” argument) says that the reason gasoline contains “less oil” is that it contains oxygenates like MTBE and ethanol. I’m not sure how MTBE is produced (it’s being phased out anyway), but most papers I’ve read on the current production method for ethanol suggest that almost as much oil is used in its production than is replaced by the ethanol. So I think UCS analysis is bogus in this regard. At the very least, gasoline requires much more energy to produce than diesel fuel (nearly twice as much per BTU according to UC-Davis).

    “Are there really diesels out there that get 70-80 mpg?”

    Not currently in production, but there have been diesel HEV prototypes that achieved a “combined” 80 mpg (gasoline equivalent!). Remember the PNGV program of the 1990s? All of the “Big Three” U.S. auto manufacturers produced a working prototype that got at least 72 mpgge (largely funded by the U.S. government). I have to wonder why they were never pursued for full production? It wound up being nothing more than an interesting R&D exercise.

  • dieselfan

    Many years ago I was a refinery tech. Diesel required virtually no processing after fractionation. Gasoline required a trip through the catalytic cracker which was a huge furnace with gasoline and hydrogen running through its red hot heat exchanger. So I believe the energy cost to make gasoline is higher than diesel.

  • yeaperson

    Two facts: a mechanic friend decades ago said when he worked on big rig Diesels the inside was clean of carbon after 100,000s of miles. Second, I drove a Camry Turbo Diesel almost 100,000 miles; it was quiet, comfy, smooth. Diesel fuel is a lubricant.

  • Medmann41

    What blows my mind these days is thay we made it from a sputnick type of satellite to landing on the moon in like a decade….and we can’t figure out how to make a more fuel effecient engine being diesel or gas and super batteries to run eithir hybrid cars more efficiantly or all electric cars…in that 10 years while racing to the moon hundreds of necessary items and technologies were developed that were not there previously(teflon and super computers for example) but they can’t get cars in general to at least double or triple their gas milage…..what is needed is a Manhattan type project to get it all rolling …before we either run out of crude oil or can’t get anymore from the Arabs or our good buddy from down south, Hugo!!!

  • Felixx Kramer

    Diesels may be cleaner than gasoline cars on particulates, etc., but most of us these days are also paying attention to greenhouse gases. In that case, both gasoline hybrids and diesels are more efficient users of petroleum.

    In contrast, plug-in cars (plug-in hybrids and electrics) DISPLACE gasoline with electricity that both centralizes the generation of conventional emissions and reduces the generation of CO2. The August NRDC-EPRI study confirmed benefits even on our “dirty” national grid, and far greater benefits as we evolve to renewable sources of electricity. (And since electricity doesn’t come from imported oil, increased energy independence, of course, is a secondary benefit.

    — Felix Kramer, Calcars.org

  • bagwell

    I just a 30 mile range for my commute and I’m set! no more Exxon or Shell.

  • Bubba Hotep

    What I have not seen mentioned here is that a diesel engine does not have to run on petroleum based diesel fuel. Unlike a hybrid vehicle, which does require petroleum based gasoline, a diesel engine can run on fuel made from renewable resources. With little to no modification a diesel can run on, “bio-diesel,” or with a little more work it can run on straight up vegetable oil.

    The biggest problem with producing a more fuel efficient vehicle is not a lack of technology or skill, but rather, a lack of will. Remember the Geo Metro? I bought one of those in 1993 and consistently got more than 50 MPG on long distance highway driving. Around town I got around 45 MPG. At the time I was also considering a Honda Civic CRX HX (or something to that effect) which was advertised as getting somewhere in the neighborhood of 55 MPG.

    Neither of these vehicles used advanced, hybrid technology. Instead they were small, light and used small, efficient engines.

    The vehicles current offered in America are too big, too heavy and way over-powered. I one talked to a gentleman from west Africa who told me that the mini van he drove in the U.S. had twice the horse power of the typical public bus used in his homeland.

    Do we really need all of that power?

    Mazda recently released the 2008 Mazda Demio in Japan. The 2008 model gets 23km/l which works out to about 54 MPG. How does it achieve this number? A small, fuel-efficient gasoline powered engine in a light-weight, aerodynamic body.

    (Wish I could import a Demio to the U.S.!

  • frans

    i didn’t hear that !