Here is why they may be in your future and why they can get such high fuel economy

If you think of diesels as the smoky, slow car from the 70’s, think again.  Today’s diesels are clean burning, powerful, and reliable.  The newest common rail technology cars are so quiet and clean that a bystander would never know the car is a diesel by the sound or smell.

In fact, there’s less soot on the exhaust pipe of the latest TDI clean diesels (the VW/Audi marketing name for diesel) than many comparable gasoline cars!  Diesels account for about 50% of all new car sales in Europe and have much better fuel economy than a similar gasoline car.  For example, the VW Lupo, a Europe-only subcompact Volkswagen, drove 20,000 miles around the world in a promotion, averaging over 80 miles/US gallon (2.5 liters/100 kilometers).

A major concern for modern cars is improving fuel economy and emissions, so diesels will have a much larger market share in the short term North American market.  Audi, VW, BMW, and Mercedes Benz all currently have multiple diesel models for sale in the US.  In the long term cars will probably be hydrogen fuel cell or fully electric powered.  In the far future we’ll all be flying around on personal jetpacks circa the 1962 world’s fair.

Volkswagen Audi TDI in North America are turbocharged and intercooled 4 or 6 cylinder engines that use direct injection, a technology that is only now being put into a few gasoline cars.  Larger/sportier diesel passenger cars like BMW or MB and trucks use 6 or 8 cylinder engines.  The largest engine for North American TDI was the twin turbo V10 in the Volkswagen Touareg.  Europe even had the option of the V12 VW Touareg TDI and Audi Q7 TDI!

Some of the major reasons why diesel engines get better mpg is because of the engine design and fuel.  Diesel fuel contains more energy per gallon and run very lean (a higher air:fuel ratio) so they can do more work off less fuel.  The combustion process also produces less waste heat, meaning more of the energy is translated into work.  All diesels are high compression so the engine can get more energy out of each combustion cycle.  Engine RPM is controlled by fueling and not a throttle, meaning parasitic pumping losses off the engine are reduced.  Modern diesels are all direct injection, meaning the fuel is compressed under very high pressure and sprayed directly into the combustion cylinders.  They are also all turbocharged, which can increase fuel economy, depending on engine design and power load.

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