MPG or mpg is a three letter abbreviation with multiple meanings, including:

• miles per gallon, see fuel efficiency. Used alone, "mpg" is ambiguous, because US and imperial gallons are significantly different (quoted vehicle fuel efficiency is therefore significantly different for the same vehicle in the US and UK). Miles per gallon is the common measure used for fuel efficiency in the UK even though all road fuel is now sold there in litres. An unambigious measure is kilometers per litre (km/l though it may also be found written as kpl).
• MPEG – MPG is a common shortened file extension