This is an attempt to calculate the efficiency of a modern gasoline engine (Volkswagen's 1.6 litre FSI). The result seems too good to be true. Please let me know if there is any error. At a constant 100 km/h on a flat motorway, the consumption of my car reads 5.7 l/100 km. The engine revs at exactly 3500 rpm. From the power curve below, the power output at this rpm is 54 kW = 54000 joules per second The consumption of 5.7 l/100 km at 100 km/h translates into 5.7 litres per hour, or 5.7 / 3600 = 0.00158 litres per second. Therefore the energy per litre is 54000 joules / 0.00158 litres = 34.2 megajoules per litre According to wikipedia, "gasoline contains about 34.6 megajoules per litre": http://en.wikipedia.org/wiki/Gasoline Therefore the efficiency of my engine is: efficiency = output energy / input energy = 34.2 / 34.6 = 98.8% But someone said internal combustion engines have a typical efficiency of 15-20%. Was that about old technology in fact? Or is the 1.6 FSI so incredibly efficient?