Problems not found in a UOA

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Dec 20, 2002
The coal hills of eastern PA
What types of problems could arise if you use an inferior engine oil (compared to top tier synthetics) that would not show themselves on a UOA. For example, if you use Pennzoil 5W30 dino and all wear metals are in the low single digits for a 5,000 OCI, is there even a need to run synthetics other than prolonging the change interval? What other factors of an ill engine do not show up on a UOA? Does a great UOA with little wear numbers show that your using an oil that is good for your engine?

[ May 30, 2004, 05:30 PM: Message edited by: ryansride2017 ]
I'm surprised the 'experts' aren't posting a reply to this question as it's been my question too for a long time.

If I had to guess I'd say a UOA will only show you what's actually coming out of your engine and not what's not. In other words, a certain oil may give great UOA's, but your engine may be developing sludge and varnish that could only be seen by disassembly. Jerry mentioned this before. I haven't seen him posting recently.
Thanks Dr. T. It's a rather hard question to phrase, that's why I figured I didn't get a respone. I just wanted to know what reason would I have to use synthetics if a UOA on conventional oil looks fantastic at a relatively long O.C.I. (5K)? What else could I be missing (by using dino oil) that a UOA doesn't tell you. I figured if the engine was sludging the solubles % would be high. The only thing I could think of was an additive in synthetic oils that would keep seals from leaking a little better than dino oils.
I think the cleanliness will not be as good and there will be more deposit buildup. I personally believe that the amount of wear on the engine will be less with synthetic. But I would be hard pressed to prove it. I guess I would have to default on some information that Mobil 1 published which showed origional crosshatching in the cylinder at 200+ K miles.

Also under adverse conditions-both high and low temps-the synthetic should provide some margin of safety. If you somehow ran your engine longer than you should have with a broken radiator hose, you would probably be better off with a full synthetic in there.

I'm guessing that the difference in the longlivity of the engine would be very slight when comparing syn to non-syn.
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