#### DENSITY

Density is another property of gasoline, which can affect your fuel economy. It indicates how much chemical energy the gasoline contains. Density is generally measured in BTU's per gallon (the BTU, or British Thermal Unit, is a standard unit of energy), and usually varies less than 2% among most gasoline but can vary as much as 4–8%. This indicates that gas mileage could vary by as much as 4–8%, depending on the density of the gasoline you happen to choose.