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Diesel Urea Injection: Fact and Fiction

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2009 Mercedes Benz GL Class 3.0L BlueTec

2009 Mercedes Benz GL Class 3.0L BlueTec

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Myths abound about the new generation of clean diesels set to sweep the marketplace this fall (Mercedes E, R, ML, and GL, BMW 3 Series and X5, Audi Q7, Q5, A4, A3, VW Jetta TDI). In an attention-getting headline, our sometimes cynical peers over at Jalopnik blasted this one today: "New Benz BlueTec Diesels Won't Run Without Urea." True? Err...kinda. Attention-getting? Bingo. Hey, it's election time, so we're used to quick soundbites that grab the attention. But just like political prose and negative campaigning, we'd advise a much closer look.

1) Mercedes' new 50-state legal 3.0-liter turbodiesel V-6 engine, which goes under the trade name BlueTEC in its E-Class, R-Class, ML-Class, and GL-Class vehicles, does not need urea to run. Period.

2) The new BlueTECs do need urea to meet U.S. emissions standards, and as such M-B brokered a deal with the EPA to ensure that if the seven-gallon urea tank goes empty (seven gallons are expected to last roughly 10,000 miles), the vehicle's emissions systems will only allow 20 additional starts until your Benzo says, "No mas!" So, supposing you've completely ignored the array of warnings, lights, and readouts telling you to head to your local M-B dealer to get the urea tank refilled, yes, you'll get exactly 20 more starts and not one more.

3) We suppose, if you're ultra-stubborn, you can do what schoolbus drivers in Detroit and Minneapolis do in January, and leave your Benz diesels idling all night long (in the case of the former, so the old low-tech bus diesels won't refuse to crank on the bitterest of mornings). You could, indeed, save those 20 starts for 19 oil changes, and just leave the engine running interminably. Diesels are ultra-efficient at idle, where they also don't produce a big thermal load on the cooling system, so she'd purr happily away while you sleep. And you'd never have to change the urea for, say, 200,000 miles. Ha ha! Take that, Uncle Sam and the EPA!

Or, simply, having decided to purchase one of Mercedes-Benz's new efficient, torque-rich, and extremely clean BlueTEC diesels, and enjoying highway milage in the mid-to-high 20s in your 7-passenger, 5,000-pound-plus GL320 BlueTEC SUV bruiser, or mileage solidly in the 30s on your posh E320 BlueTEC, you could have the service techs top off the urea every time you get the oil changed. I'm just sayin'. Seven gallons in 10,000 miles sounds a small price to pay for ultra-clean emissions and at a reported cost of $7.50 per gallon for the urea, it doesn't sound like a cost that's out of bounds for the average Mercedes owner.

Diesel has an uphill battle here in the Unite States, but with our open ear and open minds, perhaps U.S. drivers will open their driveways again to the notion of, say, a VW Jetta that can get 58.85 mpg in the right hands. Diesel is not THE answer, of course. But I think it's one small part of the solution, and I hope it gets a fair shake this time. Diesel got killed the last go-round by the clap-trap GM Olds 350 diesel. Let's hope it doesn't get killed this time around by misinformation and knee-jerk headlines.

I'm Colin Mathews, and I approve of this message. Haters, get your pens and keyboard ready.--Colin Mathews
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Comments (8)
  1. Colin: Good info I hadn't seen before, thanks for the hard facts.
    FWIW, here's my take on diesels:
    (1) They're popular in Europe not because they're ultraefficient, but because diesel has been heavily tax-advantaged for years, since French truckdrivers went on strike in the late Seventies if memories serve.
    (2) Setting aside issues of whether my Mum wants to tank up next to semi drivers (that's a fixable problem), the big unknown for diesels are:
    - short term: price of diesel v gasoline
    - long term: health impacts of nanoparticulates
    With so much efficiency left to wring out of existing gasoline engines via GDI, downsizing, turbocharging, etc., I'm less bullish on passenger diesels than I was a few years ago.
    They may indeed, as you say, form part of the solution. But will they get above, say, 10% of the light-duty vehicle market? I'm not so sure. We'll see.
     
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  2. WRONG. TOTALLY WRONG. Diesels are EXTREMELY EFFICIENT AND EXTREMELY DURABLE, that'sx why all TAXIS in Europe are Diesels, not just 50%+++ of all privately owned cars.
    You need to get your facts straight. And EPA is NOT helping, its new (and old) MPG Ratings are a JOKE, you cannot even use them for COMPARISON, because it still heavily UNDER estimates the MPG of DIESELS and OVERestimates that of hybrids.
    You should NOT believe in any EPA numbers for cars such as the VW Jetta DIESEL. It is EPa rated 30-41 or 29-40 with auto, BUT it gets ON AVERAGE 40.7 REAL MPG, ACTUAL consumption (Motorweek test) and in popular MEchanics against the Prius, the Jetta Diesel was BETTER by 1 MPG on the highway! (46 vs 45 I think).
    ANd of course there is NO comparison in DRIVING PLEASURE between the wimpy, pathetic hybrid and the TORQUE-Rich Jetta Diesel with its excellent handling and performance.
    So far, US diesels are only a little more expensive than their gas counterparts, and with the Fed Tax credit o $1,300, you can save $ IMMEDIATELY! No need to drive 250,000 miles to do so, as with some HYBRIDS!
    DO THE MATH. and FORGET the old, DIRTY Diesels, running with the OLD DIRTY fuel. Get up to date on what is going on NOW.
     
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  3. I read in the last Popular Mechanics issue that chemists have developed another synthetic diesel that is much more pure than conventional diesel. This results in significantly lower emissions (a couple of orders of magnitude) while the energy density is just as high. (I threw it out already so I can't give more details, sorry)
     
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  4. Tom: They can already make excellent, very clean Diesel fuel from Natural gas. Qatar, which is a tiny island, but has enormous nat gas reserves and huge LNG terminals and fleets, is already doing it. It's called GTL (Gas to liquids) tech.
    Russia has the world's largest nat gas reserves, at 1,600 trillion cubic feet, then iran at about 980 trillion and Qatar a close third with 905 trillion. Today the three formed a nat gas "troika" cartel thing, (saw article in the news) that would give them more than half of the world's nat gas reserves.
     
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  5. Diesels now are extremely clean with particulate traps employed on new diesel cars produced now. Peugeot was the innovator here with the first car with a silicon carbide particulate filter made by Ibiden in Japan. Since then Coning now produces a diesel filter with a patented ceramic composition. http://www.corning.com/environmentaltechnologies/products_services/particulate_filters.aspx
    Together with engine management technology, filters and cleaner fuel the diesel engine can be as clean as gasoline engines. The greenhouse gas carbon dioxide is also lower for diesel engines so there are benefits there.
     
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  6. That still belies the price jump of diesel in the winter, when it competes with home heating fuel...I have seen diesel jump to $1/per gallon more than premium. Additionally, diesel is not universally available at military bases in California....a cultural thing, I assume
     
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  7. I've only owned an old MB diesel for about 5 years now but I have never seen diesel anywhere near that high... it should be the cheapest, even with the new ULS requirements but it does tend to be slightly above or below premium (never seen worse than about 30 cents higher and have seen it cheaper than 87 on occasion, personally). As for not being available on military bases...who cares? I fill up on base when it is convenient for me but its not like you're saving a ton anyway, maybe 5-8 cents a gallon...big whup! Even above premium prices my 30 year old diesel car gets better mileage than most of the cars in current production (esp. if I keep my foot out of it) so it's still much cheaper to refuel than a gas car.
     
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  8. I honestly dont think the price of diesel will ever be lowered in the US accordingly and reflect that it is cheaper to produce and therefore cheaper to buy.....thats the real stimulus for ownership... as well as greater extraction of BTU.....generally I dint think the US auto industy want them....
    it would be another shot in the arm for the US auto industry as the Euro companies line up with more of their proven technology....
    As for driving modern low sulfur diesels......absolutely superb !!
     
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