Problems not found in a UOA

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.


Thread starter
The coal hills of eastern PA
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.


Elizabethtown, Pa
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. [Smile] I'm guessing that the difference in the longlivity of the engine would be very slight when comparing syn to non-syn.