Just curious, for those of you that do an oil analysis (I have never done one) how does it tell engine wear?

 

I have done a few with black stone and won't anymore. Because after 5,000 miles or so with m1 and normal DD driving, the answer always comes back:

"Looks good you can go another 7,000 - 9000 miles on this load"

Yes, you read that right, most Mobil 1(and others) are good for 10-15k....

We (including me) way overthink this oil thing, I don't anymore, and just change at 5-7k /1 year when convienient .....

Sample:
http://m.blackstone-labs.com/ReportExplanation

 

The oil testing fans believe the trace levels of various metals in the oil tell how much metal is scuffing off bearing, cam, and other moving surfaces in the engine. They would say that higher level of metals indicates more wear. I’m a chemical engineer retired after a career in refining from a major oil company, and that included exposure to actual engine testing for improving fuels and lubes. We found that there is essentially no correlation between used oil analyses and actual wear in engines measured by tearing them down and literally measuring the wear with micrometers after tens of thousands of miles. When I say “essentially no correlation”, it means that once in a great while, massively huge amounts of metals in used oil did indicate a major failure was about to happen. But modest variations, which are what happens almost all the time, are useless as wear indicators. There are too many places other than the used oil where wear metals can end up, such as filters, sludge, and thin coatings on various internal engine surfaces.

That’s why the major oil companies still do the very expensive engine testing to develop their fuels and lubes. It costs a ton of money to run a car in a test cell for tens of thousands of miles, then tear apart the engine and inspect it. But it’s the only sure way to know whether your fuel or lube is really performing. While I seldom badmouth other oil companies and never promote my own, I will say that I recommend using fuels and lubes from the big boys because they are the only ones who can afford to back their fuels and lubes up with proper engine testing. That doesn’t rule out the possibility that there are some fine oils coming from some of the little guys. It simply says they go more by the seat of their pants rather than hard core engine testing. As long as their expert’s pants have good seats, that’s fine, but as an engineer, I prefer hard core engine testing data.

 

Oil analysis can/will tell you if the additive package is used up.

 

In normal street use, the Oil Life Monitor on the C7 will go at least 8 - 10,000 miles in between changes (assuming the time calculation doesn't get you first), and there's a good 100% margin of error built in. For moderate driving with a high quality synthetic oil you could probably go close to 20,000 miles between changes without worrying about engine damage as a result. I've personally seen BMWs go 15,000 miles before the car says it's time for a change.

 

Seems like a misleading claim to me. Yes, analysis can show the presence or absence of various elements that are usually associated with additives. But it doesn’t tell whether the additives are still in effective form or have broken down. For example, elements like phosphorous and zinc are normally in anti-wear additives, but they are present as very complex organo-metallic compounds. Once those compounds break down, the additives are no longer effective, but the phosphorous and zinc are still there. So the analysis may show that phosphorous and zinc are still present, but it doesn’t say a thing about whether they are present as effective or ineffective compounds.

I will concede that there a few tests, which if you flunk, show serious oil deterioration. But odds are, if you are worried enough to do oil testing, you aren’t leaving the oil in anywhere near long enough for these to happen. The two most serious that are also reasonably likely (or at least not ridiculously unlikely) to occur would be loss of pH buffering capability in extra long life oils, and loss of VI improvers in ultra wide spread oils (like 5W-40, with a 35 spread between W and plain number). Trouble is, I’m guessing that most oil analysis companies wouldn’t give a layman enough background to interpret those properly even if they did measure them. My advice is, use an oil that is both full synthetic and meets Dexos spec (quite a few oils are one or the other but not both of those two), stay with 5W-30 even in hot weather unless you do honest to goodness racing, go with a major oil company that has enough funding to back their product with real engine testing, change it somewhere in the oil monitor’s 0-30% remaining life range, and don’t sweat the rest.

If you are one of the special purpose folks who use the car for both track and street, your decision on weight gets tougher. Blueray16’s idea of swapping and saving oil has some appeal, but is inconvenient and has contamination risk as you change it out. So I don’t have an easy answer for you. I would say that if you try to straddle by using ultra wide spread oils like 0W40 or 0W50, don’t leave them in too long. Even full synthetics over a spread of 25 must use VI improver, and that additive is prone to degradation. What’s worse is that if it degrades, VI improvers work such that they degrade on the high end. So for example, 0W50 is basically 0W25 with VI improver to make it 0W50. As the VI improver degrades, it slowly drops from 0W50 to 0W40, and eventually to the base oil 0W25.

 

I’d be careful of that. The limiting factor in long oil life is pH buffering. To get that kind of life you need to use an oil specifically labeled for extended oil change intervals. The main difference in such oils is an unusually strong pH buffer additive. Without that, as mileage increases, your oil can turn acidic.

 

Obviously the best way to tell engine wear is to tear the engine down and do measurements, but that's an expensive and time consuming venture too. Oil analysis can give you a pretty good idea of what kind of engine wear you're seeing, so long as you have been doing it on a regular basis with that engine. I find my oil analysis reports are very consistent in the amount of wear metals that show up, and those numbers are also low in my cars. If I ever kept a car long enough for it's engine to reach the end of it's life, I would most certainly begin to see a trend in my oil analysis reports where those wear metals that were once low, would be much higher.

When I first began doing oil analysis, I wanted to compare different brands of oils to see what differences I saw and with some oils the wear metals would be significantly higher or lower than some of the others in that same engine. Food for thought....

 

While waiting for my wife shopping, I spent some time strolling the aisle in Walmart with all the automotive oils. I was surprised to see just how many had the dexos approval. There are a lot of choices out there that would meet GM's requirements. While Mobil 1 is "recommended", there are a lot of other brands that are dexos certified.

 

Many, many manufacturers have oil recommendations for varying condition. Most I've seen recommend a heavier oil for temps over 100 F and a lighter oil for temps under 0. I would be surprised if something like this wasn't buried somewhere in the Corvette factory information.

One thing is certain Mobil 1 15w50 and 0w40 are unlikely to damage the Corvette else GM would recommend them.

 

All I can say is that if oil analysis was considered even semi-reliable as a wear indicator, nobody would do engine testing and tear down. The reason the big companies still do engine testing and tear down is that they have found cheap tests are no better at indicating engine wear than flipping coins. Think about it. If cheap tests were even slightly more accurate than flipping coins, you could run hundreds of cheap tests and average the results, and still be far, far cheaper than engine testing. I know that the cheap tests sound like a good idea, and it seems like they ought to work. Likewise, I can appreciate that you want to know about your engine condition, and I agree that it seems like some info ought to be better than none. Unfortunately, when you look at the real, hard data from engine testing and tear down, you see that it simply does not correlate with the cheap tests.

The owner’s manual very clearly states 5W30 on the street at all but very cold temps, 0W30 on the street when temps are 20 below zero or colder. It specifically says do not use other grades such as 10W30, 10W40, or 20W50 for any applications. It says 15W50 should be used on the track, but that is clearly stated “for the track”, and is very clearly not recommended by GM for use on the street. I hear what you are saying, but for my money, I’ll stick with the recommendations of the guys who designed the engine.

 

Makes me wonder if they designed a different engine for the Corvettes going to Europe.

 

There have been several threads on the forum saying that 0W40 is recommended in Europe, but I have never seen any firm evidence that such recommendations came from GM. Yes, there have been pictures of stickers on the door sill, but the dealer or importer could easily have added those. If you look on the GM-Europe web site and go to the owner’s manual section, the oil vicosity recommendations there are the same as in the US manual. The only difference is that they say if Dexos spec is not available, ACEA-C3 spec (which is a European spec similar to Dexos) can be used. But viscosity recommendations in the GM-issued owner’s manual remain the same as in the US.

 

LDB, thanks for the information, it was very informative and helpful. I do have a question for you based on your background. When Corvettes first started using Mobil 1 as their oil of choice it was 100% synthetic and no mention of Dexos. Now they recommend a Dexos certified oil and not necessarily Mobil 1. So what is Dexos and what makes it better than Mobil 1 Synthetic?

 

Dexos is not an oil, it is a set of specs required by GM , some say for business purposes. Mobil 1 carries the dexos approval, and probably did before there was the dexos scam. Many people think the blended AC oil is dexos oil, it is not, it is just another oil that carries the dexos stamp of approval.

 

You are making this far too complicated. Just go with 5w-30 Mobil 1 and you will be fine.

 

amen.......

 

When all is said and done, if you use Mobil 1 5w30 and change oil according to the oil life monitor your engine will most likely make it to 300,000 miles without any oil related issues whatsoever. And how many people on here will even put that many miles on their C7s?

 

Hmm. Just checked the net and 5 quart jugs of Mobil 1 0-30 and 15-50 are $23.88.
With the cost of a track day, cost of tire wear etc, is and extra $50 (assuming a dry sump) worth the effort to save it? One hard dirt/sand particle could scratch a bearing etc.

 

Ill try my Mobil 1 diatribe!
Check out this article from and old Car & Driver mag: http://www.caranddriver.com/columns/...mantics-column
Prior to ~2000 Mobil and many others made what I'll call for this discussion a "true synthetic oil." As the article points out these were produced with man-made molecules called polyalphaolefin (PAO) base stock, which made up a majority of what was in the bottle. Castrol, started labeling "synthetic" in essences a more highly refined, what some call Dino oil (coming out of the ground.) Mobil tried to get them stop bringing a "false advertising complaint." They lost! As the article points out the Castrol type product costs manufactures about 1/2 what the PAO base oil cost! They all switched!
I have been using Mobil 1 since 1974 where is solved several problems in my 260Z and modified Corvair (14 inch wheels, HD suspension, quick steering etc.) I still use it and it is as good as any other oil IMO! It is no doubt better than some of the "no-brand oil" that meets dexos 1, a GM spec for which the companies pay tribute to GM! In fact Mobil resisted for a short wile and would not pay GM! They pay for marketing reasons the oil is no different it no doubt met the lesser GM spec all the time!
I wondered why Mobil prices reduced significantly after ~2000!! Just recently found the referenced article with a very good explanation. As he starts off referring to the Clinton/Wolinsky tryst at the time it was written, "Now that the meaning of "is" has gotten so slippery..."