If you use good quality fuel and when you service your car you fill the tank and add the correct amount of RedEx or something similar, you shouldn't even need to De-coke the engine. Some people recommedn an oil flushing agent every 3rd service but don't, regular oil change is enough! A small build up of carbon can be good for the inside of your engine as it can take up some of the clearance on worn bearings. Never EVER use this sort of stuff on a high mileage car! It may clear the crud out of your hydraulic lifters cureing noisy tappets but it will also clear out any carbon deposits in your bottom end bearings leaving you with a knocking motor.