Oil Analysis

[Elizabeth Ann]

Do any of you guys send your used oil out for analysis? We've been sending our oil out yearly (or with every change) as a 'preventative' screen.

I'm wondering if this is necessary or just a waste of money?

[rt11002003]

Oil analysis is done by most commercial aircraft operators and by commercial diesel truck operators. Their goals are long engine life and reliable operations. The reason, of course, is economics.

Considering the cost of engine overhauls or replacement it make sense to keep track of what's going on internally and perhaps detect problems before they become serious.

Magnetic drain plugs used to be the rage and may still be. However, by the time one finds bits and pieces on the plug it may be too late. And the plug only catches some materials.

It seems to make sense to me.

Gene

[Mariner]

I purchase a kit and send in a sample from every oil change. But I've yet to receive anything back from the company that supposedly does the test. I'm actually pretty damn upset with them.

[Elizabeth Ann]

We use HO Penn and we get an analysis back. At least we used to.

[RicM]

There have been extensive postings on this topic on boatdiesel.com. Land based diesel fleet operations use the testing to extend oil life and predict rebuild intervals before failure occurs. The general consensus is that for recreational boat users it's much more cost effective to just change the oil at much more conservative intervals. Land based diesels run many hours five days a week. Marine diesels run much harder but for, on average, 10 hours a week? Completely different use cycle. Damage to marine diesels is more likely from lack of use, oil draining from engine leading to rust, corrosion etc. Testing facilities are looking for chemical breakdown in the lubricant and traces of metal in the fluid. In a typical marine application you are nowhere near the end of the oils lubrication, you are just trying to get rid of carbon and other crap that collect in the oil.

[Mariner]

Agreed. Bust still, for $15, why not do it?

[RicM]

Because without a baseline and a series of tests at intervals it doesn't tell you anything. One oil test cannot tell you anything, it's a means of tracking engine changes over many hours of operation.

[Mariner]

That's what I'm saying. If you change the oil twice a year, and do an analysis each time, you should be able to spot changes if anything is going wrong.

[RicM]

I really suggest that you read the material on this topic at boatdiesel.com and decide for yourself. My take away from the discussion is this.....oil analysis does not predict engine failure, it predicts oil failure. It's use in diesel fleet operations is to maximize the life of engine oil ( major expense in fleet operations). Many of these fleets use expensive synthetics like Amsoil that can have very long service lives, and with regular filter changes that oil can be used for many times the equivilent recommended service interval on a marine engine. This will cut costs for the fleet operator, maximizing profit. The operator wants to know the precise point that the oil is starting to breakdown to replace it at the last moment. The goal is to get the most out of the oil.
A marine engine in recreational use is more likely see oil and engine failure due to lack of use rather than overuse. The use of long running 100% synthetics is not recommended in a recreational marine diesel, as it's superior flow characteristics make it a poor choice for an engine that is not run many hours a day, 5-7 days a week. Why? Because it tends to run off engine parts from Monday- Friday and when you start the almost dry engine on Sat AM and run it for 3-4 hours, the damage done when dry starting is worse than the slightly less slippery, more clingy, much cheaper dino oil. The cheaper dino oil is BETTER than the 100% synthetic for the service we are using it for.

Ok, now what is oil testing going to tell us? Other than finding metal shavings in the oil which you can do yourself with a magnet (at which point you are screwed anyway) nothing. If you were to find metallic debris what would you do? Tear down the whole engine and check to find out which part was out of spec? Unlike the human body for example, there is no immune system that reacts to disease before we become aware of the infection. Metal parts don't change their chemical nature when under stress, and there is no evidence of upcoming mechanical failure going to be present in the oil. It's not a blood test. If you change your oil at the recommended service intervals you will be way short of any danger of oil failure, and if you don't change the oil, and try to extend your oil life as described above you will be voiding your warrantee.

The oil analysis company will take your money twice a year for eternity and tell you your oil is fine according to their test parameters. They are never going to tell you that it is pointless for your use. Your engine will break down without warning someday. If you tested the oil out of a Yanmar that has just dropped a valve, the oil will probably test fine, because the test is not designed to predict a part breaking, it is to predict the point at which the oil needs replacement.

Now I suppose that in some limited situations, such as a gasket leak where coolant was getting into the oil or something it might provide an alert, but my understanding of diesel mechanics is the engine will be running really bad before that happens. Most failure in diesels is caused by bad (contaminated) fuel. The diesel fuel itself provides much of the lubrication in the fuel system and cylinders. Short of testing each batch when you top off, that's not really practical. If you want to get really into protecting your engine in a proactive way read up on the multistage fuel filtering systems at boatdiesel.com. A little obsessive perhaps, but a much better application of $$$ to protect your engine than oil testing. Once again, this was MY take away and I suggest that you read up on it yourself and come to your own conclusion.

[Elizabeth Ann]

Thanks for all the helpful discussion. I think I'll continue the analyses with every change, but be confident that a well maintained engine will provide much more confidence then the analysis.

[jcollins]

Well said Ric!

[RicM]

From the discussions on boatdiesel.com it was apparent that some folks were under the impression that they were going to get a report that said something like the sleuthing on CSI, "there's a 10% rise in molybendium molecules in the spectral analysis! Intake valve #3 is going to fail within the next 10 hours of operation!", which, of course is totally ridiculous. Oil analysis is a valid tool for fleet operations and the companies that do it concentrate on that market for a reason. You, the operator, are probably the best judge of your engines' condition. Use your senses, sniff the exhaust, listen to the sound. You know more than you think. Ever wonder why our noses are above our mouths and the nostrils point down? Because all the people born with their noses pointing the other way died of food poisoning.