To find out where to dispose of old gas, check with local government agencies and the fire department first. Most cities have strict rules and guidelines for storing and disposing of gasoline in a particular area. They can also provide resources and locations for disposing of it safely.
There are often local fire codes that prohibit storing a certain amount of gas or rules about where it can be stored. When disposing of it, it is important to do so very carefully. Gas is very dangerous when not disposed of properly. In many cases, fire departments prohibit homeowners from having more than 25 gallons of gas on hand at any given time.