Engine efficiency % improvent to mpg improvement

[Ken Fry]

Originally Posted by redpoint5

As the math shows, a 1 point increase in efficiency on a 30% efficient engine is a 3% increase in overall efficiency.
Most Efficient Diesel Engine - 50% Efficient

Which is to say, that if you have a car that gets 30 mpg with a 30% efficient engine, it will get 31 mpg with a 31% efficient engine. (If only engines actually operated at 30% efficiency over real test cycles.)