seafoam: does more harm then good
its the same as flushing a transmission... and here is why: usually if you flush an old transmission, after doing so, a couple of weeks later.....it will grenade...
why? because with wear comes buildup of "gunk" and often time that "gunk" is actually what are holding your bands together....so of course, here you come being Mr.(or mrs., lol) tidy flushing it squeaky clean.......and then your bands having nothing to hold them... bye-bye transmission
same concept on engines, now with an engine that isn't on its last leg, well, seafoam isn't going to hurt... but there have been A LOT of horror stories after running it... personally, I say keep your engine well maintained and let it ride... I know people that have had work vehicles they bought brand new last upwards of 300,000 miles... and they didn't need any stinking seafoam lol