Imho---If you like the sea-foam; use it. Won't hurt anything. The absolute best fuel system additive is BG 44k. Best to use just prior to changing the oil. Stuff ain't cheap, but i've found none better...

Put it all in you gas tank. Helped me with slow starts on my 91 300E. I also put it in Altima SER and it took care of the check engine light. If you put it in your oil, be prepared to start seeing oil leaks on an older car. It loosens up sludge and sediment deposits that may be acting as gasket material. It does work. And I despise snake oil.