Why are diesel engines more efficient?

Why are diesel engines more efficient than gas engines?

Scott J, Chicago

We get this question a lot, as people often associate diesel engines with semi-trucks and large pickups that don’t seem to represent fuel efficiency. Yet diesel passenger cars on the market now, like the Volkswagen Jetta TDI and Mercedes-Benz E-320 CDI, do have gas mileage ratings on par with much smaller compact cars that use less-powerful gasoline engines.

According to an Automotive Service Excellence representative, diesel engines — whether in a semi or a Jetta — are more efficient because of the diesel engine process, which burns fuel at a much higher temperature than regular gasoline engines, promoting more-efficient fuel combustion.

Also, diesel fuel has a higher energy density than standard gasoline, meaning it takes less fuel to provide the same power as standard gasoline.

There are a couple of reasons why diesel engines in passenger cars haven’t gained popularity in the U.S., even though they are efficient. Besides the fact that not every gas station has a diesel pump, there are also the stigmas of soot-puking tailpipes, oily fuel residue and noisy engine clanking associated with previous generations of diesel cars. Today’s modern diesel passenger cars are surprisingly quiet, as well as clean burning, and produce little or no tailpipe soot due to advancements in engine technology and the new clean-diesel fuel that is now the only diesel fuel sold in the U.S.

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Answered by Joe Bruzek on May 4, 2007 in How Does That Work? | Permalink

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