Diesel Automatic Cars For Fuel Efficiency

Diesel automatic cars are known for their better fuel economy than cars with gasoline engines.  The reason they have better economy is because of the efficiency of the engine.  This means more of the BTU’s in the fuel are transferred to mechanical energy with a diesel engine than with a gas engine.

This is easy to see by measuring how much energy is lost to heat instead of useful work.  Take two cars with the same engine displacement, one a gasoline engine and one a diesel engine, and let them run side by side.  You will find that the fan on the gasoline engine will have to start quite a while before the fan on the diesel does.  This is because the explosion in the gasoline engine cylinder wastes more energy than the corresponding explosion in a diesel cylinder.  Thus, there is more energy available to move the car down the road with a diesel per set amount of fuel.

Another benefit of the diesel car for years was the fact that diesel was a by product of oil refining and thus was not as expensive as gasoline.  That was until everyone started to be interested in diesels.  Suddenly, a gallon of diesel was worth the same or even more than a gallon of gasoline.  The price advantage was completely ruined.

A diesel automatic car is still a better fuel economy auto than a gasoline automatic car even though the fuels cost about the same.  You can expect to get several percentage points of better mileage with the diesel.

Of course, an automatic will not get quite the fuel economy that a four or five speed will.  Often times, there is a loss in fuel mileage of up to 20%.  Of course, this is offset by the fact that automatics are so much easier to drive.  I would never go back to a manual transmission because I really like driving around without having to push in a clutch all the time.  If I lose a few percentage points of mileage then it really isn’t that big a deal.  I like the fact that I can roll up to a stop sign and then take off again without having to shift gears.

Actually, when you combine the fuel economy of diesel automatic cars with the ease of driving found with an automatic you are still beating the economy of a gasoline engine with a clutch.  It seems to me that these cars offer the best of both worlds.

3 comments to Diesel Automatic Cars For Fuel Efficiency

  • Fairly entertaining post. Couldn’t be written much better. Browsing this post reminds me of my old friend. She always kept babbling about this. I will forward this post and I’m pretty sure it will be a good read for ‘em. Thanks for sharing!

  • Jared

    i am searching for an automatic diesel car to buy. however most car are either standard or gasoline powered. there doesn’t seem to be many cars with the Diesel Automatic combo. is this true or am i looking in the wrong places?

  • Albert

    You are right, for some reason a lot of diesels are manuals but some companies are starting to offer more automatics. Mercedes always has and VW.

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