Originally posted by Gurkha:
FI cleaners are mild abrasives so its better to use them as needed or once a while as preventive, its better to use fuel from good sources and the only additive that can be added regularly would be gas treatment.
Abrasive fuel additive??? Who makes that? All fuel additives I know of are solvent based in one form or another. I know TRC's fuel additives have no abrasives and I can't really imagine anyone who would offer one.
The two main types of fuel additive delivery systems, they are the fuel tank pour in and the "true" fuel injection system cleaner. I'm very familiar with the 3M fuel injection system cleaning system as I used it for years as a mechanic. What I call true fuel injection system cleaners are done by repair shops and not the normal shade tree mechanic. It involves disabling the vehicles fuel pump and hooking up a pressurized can of very high solvency additive to the fuel rail. The engine is run until it shuts off (runs out of additive). Caution must be taken when using this type of additive as it will strip the paint off your car.
The 3M kit comes with a pressurized can of cleaner, a can of throttle body cleaner and a bottle of fuel tank additive. For a badly fouled fuel system the 3M kit always worked great for me with great results.
The fuel tank pour in type works more by gradually softening the deposits and over the life of a tank or two of fuel deposits are gradually diminished. It is used more as a preventative maintenance item which prevents bad deposits in the first place. The best advice as to how often to use them is to go by manufacturers recommended mileage intervals. Some are used with every tank full and are multi-purpose. Others are used every couple of tank fulls.