Adding Sea Foam to your crankcase really does help smooth out old engines, and cleans them in the process. it is completely safe to use in the oil, and is stated as such right on their label. I've used it in a few old engines now and have been impressed every time by how much quieter and smoother running they get. It doesn't do anything for oil consumption though. In fact, it may even make it worse after it cleans the old sludge away from areas that can allow the oil by to be burned off.