The fact that you drive a few blocks before the light comes on leans me more toward water in it <img src="/forums/images/graemlins/barf.gif" alt="" />. If it is contaminated with water, the oil will foam when it is stirred up, then settle down after sitting awhile. Best thing is to just get underneath and check it. <img src="/forums/images/graemlins/kewl.gif" alt="" />