High mileage motors need it more, if anything. My old motor seemed to build up carbon at a very high rate, and I could use seafoam every week and see significant results. She finally blew an apex seal at 213,000 miles and was raced regularly up until the day she died. I think the most important thing is keeping the seals moving freely, so they don't start getting carbon jammed in behind them and get crushed against the housing. But once again, this is just my opinion.

Jeezus and I don't seem to agree on much, do we? lol....