Automobile fuel efficiency is most commonly expressed in terms of the volume of fuel consumed per one hundred kilometres (L/100 km), but in some countries (including the USA, UK and India) it is more commonly expressed in terms of the distance per volume fuel consumed (km/L or miles per US or imperial gallon). This is complicated by the different energy content of fuels such as petrol and diesel. The Oak Ridge National Laboratory (ORNL) states that the energy content of unleaded gasoline is 115,000 British thermal unit (BTU) per US gallon (32 MJ/L) compared to 130,500 BTU per US gallon (36.4 MJ/L) for diesel.[11]