How does the vapor pressure of aviation gasoline compare to that of automotive gasoline?

The vapor pressure of aviation gasoline is lower than that of automotive gasoline primarily due to the composition and intended use of the fuels. Aviation gasoline, also known as AVGAS, is formulated to provide stable performance in high-performance engines that operate under a wide range of altitudes and temperatures. This stability is crucial because fuel vaporization at high altitudes needs to be carefully controlled to avoid engine performance issues.

By having a lower vapor pressure, aviation gasoline minimizes the risk of vapor lock, which can occur when fuel vaporizes in the fuel system and inhibits proper fuel flow to the engine. On the other hand, automotive gasoline is designed for different operating conditions and typically has a higher vapor pressure, which aids in efficient vaporization during combustion in relatively stable atmospheric conditions encountered by cars on the road.

This difference in vapor pressure reflects the unique requirements of each type of fuel and their respective applications in aviation and automotive engines.