Originally posted by Halscion@Feb 14 2005, 02:12 PM
Lo Bux,
So you switch to synthetic after 10k? Which synthetic do you use? Do you think it matters between the cheap stuff at Walmart or Mobile One?
Do you have any links to studies showing longer engine life using synthetic oil?
I'm at about 11k now and am thinking about switching. I'd like to get 250k+ in 5-6 years, 90% highway miles.
Thanks for your response.
If I'm going to switch to synthetic, I do it immediately after completing break-in. I haven't done that with IIP and I don't plan to do it with FM until I get my three free oil changes. Then I'll just go to Wal-Mart and buy Mobil 1 10w-30 (I don't like 5W-30, it's not as stable as 10w-30, and don't need it for where I live) and call it a day.
This article by a highly respected oil analysis lab really says it best.
There used to be a number of links off Mobil's site for the million mile engine, and there are lots of testimonials on Amsoil's web site (yes, Amsoil is also a good synthetic). I run Red Line in my Supra, and I have always run Red Line in performance applications, just my personal preference, but I've also used Amsoil and Mobil 1. They are all good choices. Any synthetic is more stable than conventional oils, but to be truthful, the latest API standards are very difficult to meet, and any oil meeting
SL or SM designations are excellent oils and exceed all manufacturer's requirements. It would be hard to go wrong with any oil meeting SL or SM specs.
The biggest plus to synthetics is for turbo'd engines. Turbos kill oil, especially after shutting the engine off when the housing is still recovering from high boost. The turbo will "coke" the oil, which means it turns into a fully oxided hard carbon deposit instead of flowing back into the oil pan. Coking can cause a plain bearing turbo to seize, and can damage the bearings in a ball-bearing turbo. Synthetics don't coke. That's why they are best for turbo engines.
Without a turbo, the only thing you'll notice is a slow build up of varnish (I call it "the brown death") over time. It really doesn't hurt anything, and most mechanics rightly consider it normal. The only time it's really bad is when the oil turns black and forms a hard deposit. Pretty unlikely in our engines if you just follow the published maintenance. There is no reason to believe you won't get 250k without a rebuild in 5 or 6 years.
The only caveat to that is valve stem seals. They have been a consistent problem for Toyco (and most other manufacturers) because keeping oil out of the combustion chamber is a big deal for emissions control. So they fit seals that work really well for the first 120k or so, then you start to see a puff of blue smoke in the morning when you first fire the engine. Supras are notorious for this, especially ones running a lot of boost because heat is what helps kill the seals quickly. Lots of boost means lots of heat, so the exhaust valve stem seals slowly die as evidenced by the puff of blue smoke. Eventually it gets bad enough to require service, and there are any number of special tools available to replace valve stem seals without removing the head. In the past, it usually meant the head came off and got rebuilt. Not anymore, primarily because stem seal leakage is so common now.
Anyway, that's the long and short of it. Sorry the post is so long winded.