I travel to the US a lot and buy seafoam over there, a mate of mine over there uses it in his twin chevy engined boat and he suggested i try it....6bucks a pint instead of 20 quid over here. I have used it in fuel systems for bikes for a while now. I had patricular sucess with it on my 1980 kawasaki z250 that was a bugger for carb blockages. I dosed the tank and ran the bike for about 30 mins and left it to stand for a weekend, then topped up the tank and it ran like a dream. If i pick up an older less loved bike (kind of a mission for me) then i always dose the fuel system with it, always seems to smooth carb running, just done it on a 43f xt and its made starting a bit less 'grumpy'.
I am not sure I would add it to oil as a flush though......i am always a bit worried about flushing agents as they can loosen off 'stuff' inside the motor that can cause more problems than it solves.