I've had positive measured results with Chevron Techron FUEL SYSTEM CLEANER, not the fuel injection cleaner, the fuel system cleaner has 3x the concentration of cleaners that clean from the pump forward. I started using it back in 85 when I was in field service and kept exact logs of calls, miles and gas based on driving 2,000 to 3,000 miles a week in NJ, NY and PA. None of the other additives like gumout, STP, seafoam seemed to do anything, however the Valvoline spray cleaner does do a really good job of cleaning the throttle body plus I like that they have an adjustable and downward spraying nozzle on the can, less waste. I also do the plugs, wires, cap and rotor every other summer, I've cut my driving to 300mi a week give or take 100 miles. Plus I have only ever used regular, I put mid grade in once when I needed gas and the station was out of regular, other than a bigger wallet hit I noticed NO difference.