dragboat:"I have used the gas treatment, did not notice any difference, but you know what? I have never noticed any difference with any additive in the fuel in a car that was running well ..."
Exactly, this has been my experience as well. I have used Red Line SI-1 and isoporpyl alcohol to clean up problems in others' cars, but not my own.
I use fuel system cleaners sparingly as a preventative and my car still runs strongly despite the 126,000+ miles on the clock. Never a day when it seemed to misfire, buck, backfire or otherise run crummy because the fuel system was contaminated.
I had the head off my Civic recently and the machine shop told my mechanic that they saw evidence of valve recession. Even in clean-running cars, a little extra upper-cylinder lube will help in keeping a car running strong (minimize compression loss) once the miles start to pile up.
I don't know how much lubrication MMO gas treatment offers, but any would help. At the rate of 2 bottles per year, I don't know if I am using enough Red Line SI-1 to make a difference. I'm currently using Neutra 131. I'm not sure of its lubricating properties but because the per-ounce cost is lower, I'm using more of it.
--- Bror Jace