We have multiple gasoline fuel additives that will provide cleaning in different parts of the fuel system. Depending on the application, the usage frequency will vary. Berryman B-12 Chemtool Fuel System Cleaner (part #0116) is an excellent preventive maintenance product for fuel injectors, carburetors, and intake valves. It should be used every third fill up. Berryman B-12 Chemtool Fuel Injector Cleaner (part #1112) will clean up dirty fuel injectors, and one bottle treats up 12-20 gallons of gas. It should be used every third or fourth fill up. (If you’re using 0116 regularly, then you could simply replace an #0116 with #1112 occasionally.) Berryman B-12 Chemtool Concentrated Intake Valve & Injector Cleaner (part #3012) is a bit stronger than #1112 and will clean up dirty fuel injectors and intake valves, and one bottle treats up 12-20 gallons of gasoline. It should be used once every 3,000 miles. Berryman B-12 Chemtool Total Fuel System Clean-Up (part #2616) is our strongest detergent-based gasoline additive and will thoroughly clean dirty fuel injectors, intake valves, and combustion chambers, and one bottle treats 16-21 gallons of gas. It should be used every 5,000-10,000 miles.