I have a 98 Toyota 4-Runner SR5 V-6. I bought it with 55,000 miles on it and it now has 155,000 miles. A couple months after i bought it i was getting off the freeway and a bunch of white smoke cleared form the exhaust. I freaked out at first and a mechanic freind of mine said its probly the valve rings or piston rings that need to be replaced, but that can get pricey, $1500-$2500...So, he said just to put some Engine Renewer everytime i get a oil change and it should take of the problem. Thats like three years ago and since then i've done what he said, but every three months or so it will clear out a bunch of white smoke. It drives well, the same as my freinds 4Runner that is the same exact model and he has no problems. I saw an episode on some car show last Sunday that showed how to test your engine to see what needs to be done, but my idiot roommate erased it off the DVR.. Any ideas on what i should do as far as fixing it or just letting it go???