Purchase only the amount of fuel that will be used in 30 days. Fuel deteriorates over time. Deterioration begins with the most volatile compounds evaporating. Once evaporation reaches a certain point it will be hard or impossible to start the machine. As more compounds evaporate, the fuel will form brown gummy deposits in the system. Given enough time the gummy deposits will become a hard varnish. Gummy deposits and varnish can plug passages in the carburetor preventing the engine from running or causing the engine to run poorly (surging, lack of power, stalls, etc.). Deposits can also cause the carburetor to leak fuel if they prevent the float needle from sealing properly. Add fuel stabilizer to the fuel the day you buy it. Most fuel stabilizers form a layer over the top of the gasoline and greatly reduce the rate the fuel’s volatile compounds evaporate. They also prevent the absorption of moisture by the fuel. If fuel stabilizer is added to gasoline the day the gasoline is purchased,