my only experience w/ seafoam was really bad... i used it just like it said on the can. half in teh oil half in the gas tank. and sure enough the next day my my engine was in serious need of a rebuild.
it thinned out eth oil so it was lubricating the way it shuold and it lowered the octane ratign of teh fuel so needless to say my engine detinated. i ended up w/ a melted piston and had to rip the motor out of the car to work on it. once i got it apart i had to scrape all teh melted aluminum off the cylender walls and hone it out real well. everyoen that saw teh pictures of it told me the same thing , don;t waiste your time trying to rebuild it the motor is shot!!! of course the idea that i could repair it for less then $200 VS. a new motor for close to $1000 i tok my chances, and what do you know. she runs like a dream!!! burns a tad bit of oil. maybe 1/2 a quart every 3000 miles but that's realy not bad.
anyway the piont is if you use it be prepared for what it can do if you don't drain it out right away and or you decide to be hard on your car or truck.