How does temperature affect the density of fuel?

For every five-degree (Celsius) change in temperature, figure about a 0.5-percent change in density. Avgas (aviation gasoline) weighs about 6.02 pounds per US Gallon at 15 degrees C. That increases to 6.40 pounds per US gallon at -40 degrees C. Mogas (automotive gas) is, for the most part, the same. The density of gasoline (C8H18) is 0.694 g / cm^3 at 300 K and 0.622 g / cm^3 at 400 K. Density shouldn't change that much relative to the ground temperature (300 K =80 F). http://www.omega.com/techref/flowmetertutorial.html Reference: Engineering Thermodynamics, Volume 1, Spring 2002, Roger A. Gater, Mechanical Engineering, University of Florida