Want to go green, keep your fuel system clean. When is the best time to clean your fuel system? Every time you start your engine. PFS products are designed to clean at all times giving you the best performance, power and fuel economy at all times. Why would you want a clean fuel system just once in a while? Do you expect your best fuel economy just once in a while? Go Green Keep It Clean TM Vehicles with a clean fuel system pollute far less and get better fuel economy than with a dirty system. Do the environment and your pocketbook a favor, use PFS every time you fuel.