If you took high school chemistry, you may recall, if nothing else, that chemical reactions involve atoms matching up in certain definite numerical relationships, like dancers at a prom — at least the old type of one-male-to-one-female prom. If more oxygen atoms are present than there are hydrogen and carbon atoms for them to link up with, they remain, at the end, wallflowers. Likewise the hydrogens and the carbons. When the amounts of oxygen and hydrocarbon molecules present are perfectly matched, the mixture is called “stoichiometric” — stow-icky-oh-MET-rick. The stoichiometric ratio of air and avgas is about 15.2 pounds of air to one pound of avgas — which may be visualized as a 6-foot cube of air and a 4-inch cube of fuel.