The Modern Diesel: Green and Rewarding

Discussion in 'BMW' started by seftonm, May 25, 2009.


If there was a clean diesel sedan getting 50mpg US EPA would you consider it?

  1. Yes

    21 vote(s)
  2. No

    1 vote(s)
  1. seftonm

    seftonm Veteran Staff Member

    [​IMG] Modern diesels are far cleaner and quieter than their predecessors. Drive one and you may be surprised at how far they have come.

    [fimg=right][/fimg]Graeme Fletcher - Canwest News Service – May 13, 2009

    While not as green as most hybrids, diesels compare favorably with many gasoline cars. --Ed.

    Diesels used to be dirty, noisy and the bane of anybody unfortunate enough to have one parked two driveways down the street.

    But the modern common-rail turbocharged diesel engine is cleaner and quieter than its predecessors by a country mile. It's 30 per cent more fuel-efficient than a comparable gasoline-powered engine. The unspoken advantage, however, is the torque production at low speeds - these things will pull the skin off a rice pudding without breaking a sweat.

    The blend of positives is seeing many manufacturers bring proven diesel technology to North America - in Europe roughly half of all vehicles purchased are powered by diesel.

    Just how far the lowly diesel has come is demonstrated if you look at the BMW experience. Since the launch of its first diesel in 1983, BMW has increased the horsepower by 135 per cent, torque has risen by 170 per cent, fuel consumption has dropped by 20 per cent and the tailpipe pollutants have been reduced by 99 per cent. The diesel employed in the 2009 335d brings these numbers to life.

    The 3.0L inline six and its twin turbos dishes out 265 horsepower and a tire-shredding 425 pound-feet of torque at just 1,750 rpm. Tromp the accelerator from a standstill and the response is instantaneous. So much so that the traction/stability control system must step in to prevent the diesel from leaving a pair of parallel tracks... [rm][/rm]
    Last edited by a moderator: May 25, 2009
  2. pdk

    pdk Beacon of Sanity

    VW has a series of ads with the Mythbusters where they're addressing "diesel is dirty" claims. The ads aren't bad (can be found at and I like the angle of "diesel is ok now" instead of the other VW "diesel vs. hybrid" ad.

    Sadly, there was no mention of smog emissions or LEV/ULEV/SULEV ratings in either those ads or this article. Anyone know where to find that information, because I seem to be unable to find it?
  3. seftonm

    seftonm Veteran Staff Member

    Hi Peter, I use two sources for looking up emissions ratings. The first is, if you look up a car and then choose "Show Detailed Air Pollution Information" in the EPA Air Pollution Score part then it will list the emission standard that a car meets. The second source is from CARB and it shows the certification levels for a number of different tests and pollutants. Their test results can be found at under the executive orders listing section.
  4. wxman

    wxman Well-Known Member

    The emission category a specific vehicle hits does not necessarily reflect its true impact from an air quality ("smog forming") perspective, especially when comparing gasoline and diesel vehicles. The reason is that these emission categories only account for "tailpipe" emissions. Evaporative emissions are not accounted for in these emission categories.

    Gasoline is a very volatile substance and has much higher evaporative hydrocarbon emissions than diesel vehicles, something that's not generally not considered when evaluating emission performance of vehicles. These evaporative HC emissions include both evaporative emissions from the vehicle itself and evap emissions in the gasoline supply chain (e.g., distribution and storage of gasoline). According to EPA, there are currently approximately 475,000 TONS of VOC emissions annually from the gasoline distribution chain.

    Diesel fuel is far less volatile than gasoline, something like 1/200th to 1/500th as volatile (depending on RVP of gasoline). The evap VOC emssions are at least as reactive from a "smog forming" perspective as "tailpipe" HC emissions.

    In my professional opinion, the ancillary VOC emissions of gasoline offset the lower "tailpipe" emissions typically found in modern gasoline vehicles (with respect to diesel vehicles).
  5. scottd

    scottd Jetta TDI

    My TDI is not noisy...I think they are talking about my neighbors Dodge Ram Diesel Truck with dual exhaust. Now that's noisy, I can hear that thing a block away.

    I know my Diesel is not a "Clean Diesel" car, but I would be interested in my emissions. Based on this video from edmunds the VW Diesel is not bad for total Greenhouse Gas Emissions:

    BTW, to answer the poll: Over 4 years ago I did consider a Diesel car (I know the poll said "Clean Diesel") and I now get an avg. of 50 MPG thanks to this site.
  6. seftonm

    seftonm Veteran Staff Member

    Hi Scott, your car is better than the gasser for greenhouse gas emissions. But it is probably making much more NOx and particulate matter than the gasser. Your car is a Tier 2 Bin 10 rated vehicle. That bin allows about 10x more NOx and particulate matter than the gasser from the same year, or the new clean diesel TDI.

    You're probably correct that the article was talking about some huge truck when referring to sound. Those old Cummins Dodges made about as much noise as anything, but the newest common rail Cummins sound quieter than my car at idle. Diesels really have come that far. If you get to drive the 2009 TDI, you'll be amazed at how smooth and quiet it is. :)
  7. scottd

    scottd Jetta TDI

    I think you are right about this. I use about 20% Biodiesel, so my NOx is most likely the same, but my particulate matter is much less. I can see a difference in the exhaust smoke or lack of it most of the time by using 20% BD. Here is a site that has some data on the subject:

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