Answer to Question #73669 in Other Physics for youhao
The internal combustion engine for Mitsubishi Attrage, like for most conventional car, is highly inefficient and has a practical efficiency, E, of only 20%. Calculate the amount of heat energy that is actually released by the combustion of 1 Littre of fuel.
The energy content of petrol is about 120 MJ/gal. Since 1 gallon contains 3.78 liters so for the given case: 120/3.78 0.2=6.35 MJ. Thus, 6.35 MJ of heat energy that is actually released by the combustion of 1 Littre of fuel.