In theory, something on the order of 14.7 pounds of air to 1 pound of fuel should work nicely, and in fact, when air and gasoline are mixed in those proportions, the mixture is said to have the proper stoichiometric, or chemically correct, ratio. Unfortunately, the operative phrase here is “in theory.” In the real world, the best performance is usually obtained when the mixture is biased toward somewhat more fuel. (The amount being determined by engine temperature, throttle position and rpm.) Allow me to digress, though, and point out that the terms “richer” and “leaner,” as used to describe the air/fuel ratio, refer to the engine’s requirements and not to the stoichiometric ratio. As you’ll see, an engine fed a rich mixture of, say, 10:1, can still be lean in a given circumstance.