If you have used both products since the car was new it would be very telling if you HAD to use Sea Foam at all.
Both products, at least in my readings, seem to be the be-all end-all as far as additives go for KEEPING things clean.
OTOH, if you are using these in an older car that you don't know the history of, it would seem plausable that you might need to use SeaFoam and ARX to clean things up and then use FP and LC to keep things clean.
In my application (a 96 Taurus with 106K and bought used at 70K) I am using ARX to clean the engine. Once Im done, Ill see how things look and feel.
As far as my fuel system, I first gave it a SeaFoam treatment with little to no results. Over the course of the last 1K miles, Ive replaced the fuel filter, given it another SeaFoam treatment, dropped a bottle of SeaFoam in a 1/4 tank of gas and run it almost empty, and run 2 bottles of Techron through it, both at 1/4 tank and ran to almost empty....and noticed a HUGE difference in performance...but little if no effect on mileage.
After filling up the tank (18gallons) last fill up, I dropped 3 carefully measure ounces of Acetone in the full tank. I have yet to notice any performance gains, but it seems as though my gas gauge is moving a bit slower considering my mileage. At my next fill up, Ill know more about my specific mileage.
