Originally Posted By: ekpolk
I-4 Camrys of that vintage are known to have valve guide issues, much as some early Ford 4.6L V-8s did. If MMO somehow seals the seals, great -- use it. A good HM oil might accomplish the same end without the need for MMO. Worth trying, IMO.
I haven't had any noticeable results using M1 HM 10W-30 in reducing the cold start puffs of smoke in my '92 S-10 4.3L. I gave the oil over a year and 2K miles to do its thing, but no improvement, see this thread:
(this truck had the HM oil added last year at about 28K miles)
https://bobistheoilguy.com/forums/posts/1562871/
After reading the comments by tpitcher, I'm seriously considering trying some MMO in the crankcase, but a little reluctant, since this vehicle can sit for weeks at times with out being started. I already tried MMO in the fuel, but don't see a difference after one tank.
Note: this truck gets 80% of its use for short trips to Home Depot, etc, picking up supplies, not much highway use, so its hard to say if there has been any MPG increase after my first tank with MMO, using 4 Oz per 10 Gal.
PS: very interesting thread, I always thought of MMO as "snake oil".....