There are different types of Fuel System Cleaner available on the market which must be use at every 3200/Km or twice a month for best results. PROTEX #94300 must be use at every 5000/Km, at every oil change or once a month. The 3-in-one Cleaners (clean injectors, admission valves and combustion chambers) as PROTEX #94350 highly concentrated should be use at every 10000/Km, at every oil change or twice a year. You should use these products as soon as your vehicle hits the first 5000/Km. That way the engine will keep its performance as a new one and will get better fuel economy.