All about oil
Heavy equipment operators swear by it, logic dictates you should not run your car without it, and yet it might be less than worthless. What is it? Oil analysis. You send a laboratory a sample of your motor oil, and they tell you what shape it is in. What could be more straightforward? In theory, the presence of certain types of metals in the oil tell the tale of internal wear, while the level of contaminates determines whether you should change your oil or keep it. In practice, however, the charitable thing to say is that oil analysis is fallible.
A leading synthetic oil manufacturer (whom we will call “Brand X”) became suspicious of the results customers were receiving from an oil analysis laboratory run by a major oil company (whom we will call “Brand Y”). A sample of used Brand X oil was obtained and decanted into three identical containers. Each container was then labelled differently, e.g., “Brand Y, 2500 miles,” “Brand X, 100 miles,” and “Brand X, 50,000 miles.” The test results from these three identical samples varied from “perfect, continue to use” to “overhaul motor,” depending on the mileage marked on the sample.
A lady in Los Angeles ran errands for over an hour in stop-and-go city traffic on a scorching summer day with the temperature gauge buried in the red while the car was out of oil. When confronted with her melted-down engine, the customer claimed sabotage and demanded oil analysis to discover what foreign material had been slipped into her motor. The one quart of oil remaining in the sump was so noisome that it was almost impossible to breath inside the shop after the sump was removed. A sample of this oil was sent to a different laboratory than the one mentioned above. The test results showed nothing unusual. The prognosis: continue to use.
What’s a mother to do?
This is not to say that there are not some laboratories that can analyze oil accurately. If you want to try oil analysis, make sure the lab has a clean sample of your oil just the way it comes out of the can. As the analyses come back, keep an eye on the read-outs of the various metals the lab finds in the oil. The lab will supply you with a sheet explaining where each of the metals is found in the engine, and the significance of the amount of that metal in the oil. You might be better off judging for yourself when to change the oil, but oil analysis can alert you well in advance of an incipient problem, allowing you to perform overhauls at a convenient time instead of according to Murphy's Law.
If you use a long-drain interval oil, oil analysis becomes even more tricky. With “normal” oil changes, contaminants are removed from the engine with the oil. If you leave the oil in, changing only filters, the non-volatile contaminants will accumulate. The lab analysis of an oil left in the engine for an extended period of time could very well have red flags all over it, not because the oil has broken down, but because the contaminants have accumulated over time.
To get around this, you have to watch the rate of increase in the contaminants rather than the absolute amount of contaminants. If the rate of increase suddenly bumps upward, suspect a problem in the making.