I've never used it in the oil, although seafoam suggests you do. But I've used it as a cleaner for fuel systems in everything from lawnmowers to motorcycles, and I'm a believer. I put about half the can in with a full tank of fuel and a little less than half I pull through a vacuum line. Once you get it in, shut the truck off and let it sit 15 or 20 minutes. It basically loosens buildup so that it can be burnt up. Once you restart your truck, it's gonna smoke like holy hell! This is normal. And it's going to smoke for a while, probably 20 or 25 minutes. Don't be terribly surprised if it runs "not so great" through that tank of fuel too, if you add it to the tank. But once you get fresh, non treated gas to it, you'll know if it has helped.
Like I said, I've never used it in the oil, but I think they recommend you change your oil after ? 200 ? or so miles.
You can find other threads on here about it, and there is video on youtube of people doing it too. Hope this helps!
