Auto tankful is a term used to describe the amount of fuel that can be put into a car's GAS tank. It is usually measured in gallons and is the maximum amount of fuel that can be put into the tank at one time. The term auto tankful is often used when discussing fuel efficiency and the cost of filling up a car's tank. The crossword solution for the term auto tankful is GAS, which is an abbreviation for gasoline, the most common type of fuel used in cars.