The volatility of any liquid is its ability to vaporize, and gasoline must vaporize in order to burn. A highly volatile gasoline will help a cold engine start easily and run smoothly while it is warming up. However, the use of a highly volatile gasoline in warm weather tends to cause vapor lock on carbureted engines, Vapor lock is a condition in which the gasoline actually vaporizes before it arrives at the carburetor jet where vaporization is supposed to take place. This premature vaporization may occur in the fuel line, fuel pump, or in a section of the carburetor. When use of highly volatile fuel leads to vapor lock, the engine becomes starved for fuel and will either lose power or stall. Although refiners vary the percentage of volatile fuel in their gasoline according to season and locality, vapor lock is more likely to occur in the early spring, when some stations may not have received supplies of less volatile gasoline.