I know there are videos on Utube of ppl doing it. As a few ppl have already said, just use the brake booster line to add it. Put like half in the gas tank, then pour the rest down the vacuum line while the car is idling. You really can’t go wrong, just be aware your car will likely smoke a lot. Seafoam-ing is independent of oil changes, but if your engine is really gummed up it is possible you could get a chunk on a spark plug or kill off the O2 sensor. The product it self doesn’t hurt anything, all the crap it kicks out of engine could though.
