Definition: The scientific definition of a BTU (British Thermal Unit) goes something like this: British Thermal Unit - The amount of heat (energy) required to raise the temperature of 1 pound of water by 1 degree Fahrenheit. In the automotive world, it is used to compare the energy content of various motor fuels.
Pronunciation: bee tee yoo
Examples: A gallon of B20 biodiesel contains 127,250 BTUs of energy.