I'm with Tallsville. It's up to you how you spend your money and if fuel additives don't hurt the o-rings etc then so be it. Either 1) continued use will slowly undo the tarnish and buildup over time or 2) you will reach a point of no more benefit and pay for a placebo. I think if Lucas \ Berrymens \ Techron \ 3M \ Seafoam is used for 4 tanks of gas over 4 weeks then it may be time to fall back to the quarterly application schedule. .