Most oil companies did not market a true aviation gasoline for use in airplanes, at least after the mid-1930s, due to liability issues. True aviation gasoline is refined more carefully and filtered more that automotive fuels and practices are in place to minimize any water in the fuel.
Prior to that, airplane gasoline was not significantly different that the highest quality automotive gasoline. Oil companies beginning in the early 1920s used the designation "aviation" (sometimes "aircraft") to indicate that this was their top grade fuel, but it was, indeed, marketed through regular service stations for automotive use. The practice was largely eliminated by the late 1930s due to the potential confusion of mis-fueling an airplane with automotive fuel.
Wayne Henderson
Petroleum Collectibles Monthly
Kernersville, NC
