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U.S. Gas Is Too Dirty For Our Best Engines, Mercedes-Benz Says

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2012 Mercedes-Benz SLK

2012 Mercedes-Benz SLK

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We rarely think about what's in our gasoline when we fill the tank, but carmakers have to.

Mercedes-Benz has just launched a new direct-injected 3.5-liter V-6 engine in its 2012 SLK model, with an innovative "lean burn" mode that will also be used on a smaller four-cylinder engine.

The "Stratified" engines are far more efficient under certain conditions than conventional engines, raising their efficiency and the gas-mileage ratings of the cars they're used in.

2012 Mercedes-Benz SLK

2012 Mercedes-Benz SLK

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But the company can't bring the most advanced "Stratified" engine to the United States, because U.S. gasoline has far too much sulfur in it.

Europe has all but eliminated sulfur from its gasoline, while U.S. gas can still have as much as 95 ppm. (Separately, both regions have now rolled out ultra-low-sulfur diesel fuel, permitting advanced aftertreatment systems for clean diesel engines.)

The high sulfur level in U.S. gasoline poisons the trap that Mercedes-Benz fits to its new engine to capture the increased nitrous oxide emissions resulting from the lean-burn mode. They are periodically burned off in the combustion cycle.

In Europe, the aftertreatment system can handle the traces of sulfur remaining in that region's fuel. But in the States, it would be swamped by twice as much sulfur as it can handle, and quickly fail.

2007 Mercedes-Benz F700 Concept

2007 Mercedes-Benz F700 Concept

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Last spring, the U.S. Environmental Protection Agency was instructed by the Obama Administration to consider the effect of sulfur levels in gasoline on greenhouse-gas emissions.

Thus far, the agency hasn't reached any conclusions or proposed any new rules for lower-sulfur gasoline.

The new engines are an offshoot of the "DiesOtto" HCCI engine program first shown in 2007 in the company's innovative Vision F700 concept car.

Drivers, incidentally, will have to start paying attention to what's in their gasoline this summer, when E15 gasoline with up to 15 percent ethanol is scheduled to roll out. The new formulation is only approved for use in cars from the 2001 model year or newer.

[Ward's Auto via MotorAuthority]

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Comments (3)
  1. Mercedes is just barely getting themselves away from the "gas guzzler" tax, never might making fuel efficient vehicles. I am not sulfur is really the main problem.
    Take the C350 which is classified as a "compact car" it gets a combined 20MPG. If you look at the Prius, it is classified as a "mid-size" car (larger) and gets a combined rating of 50MPG even using the high-sulfur US gasoline.
     
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  2. dear john.... u just compared a hybrid car w a normal engine car.... wow, really?? mb is trying to get better gas mileage using just the engine alone. no hybrid system. and one of the system they came up w is "Stratified system" problem w this system is that our gas is not as clean as euro gas causing the system to chock. we r not talking about some damn hybrid system here!!
     
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  3. Rather strange that most of Europe is diesel-centric, yet MB would build a stratified system for gasoline around European gas?! Also, another interesting point is that about 65% of the world's gasoline is refined in America. Yes, different 'blends' are done here, but got news for Europe - it doesn't always take delivery of what it thinks it does in terms of fuel clarity. Overall, just another way to keep the MB stratified out of the U.S., just like Jeep kept the 5-cyl diesel out, a decade ago (under MB's reign).
     
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