I can't comment on adding ATF...I've not heard of anyone doing that before.
Quite a few people use MMO, and from what I've read of their experiences, it does seem to reduce carbon buildup. I have only used it extensively in one engine, a Briggs twin from a 580 that I thought was beyond help since it ran intermittently on one cylinder and was blowing oil overboard, probably because the rings on one cylinder were stuck from sitting. I put MMO in the oil and gas as per the instructions on the can, put in hotter plugs to keep them from fouling so quickly, and mowed 8" grass with a 50" deck for a few hours. At first, the engine was so down on power I'd have to put the clutch in every so often and let the engine and deck speed back up. After about 10 hours spread over a couple months, the other cylinder was hitting reliably, it started easier, the power came back, and the oil consumption dropped. I never had the heads off to see how much carbon there was, but it sure did help that engine.
|