I usually only use them when I am traveling on long road trips, but I know they recommend using them every time you fill the tank. Is using them the same as using buying premium gas vs. the regular?
There are only 2 that I use. Marvel Mystery Oil for top-end lubrication and Isopropyl based gas-line anti-freeze. Most of the others are just pouring money into your tank.
STP fuel additives do work. I use some form of cleaner about every five tank fulls when I am not buying gas at a national brand station (like Shell). There are the cleaner types and there are octane boosters. Both work, but unless you are a real enthusiast more then likely the octane boosters will not be doing you any real good. Some times it is a false savings, I have not done the math lately, but the last time I did, it was cheaper to just buy the better gas then to buy the cheap gas and add additives.
