ome years ago I was invited to give a talk to a yacht club about marine engines. I decided to discuss oil analysis, and prepared what I thought was one of my better presentations.
Unfortunately, about half of the audience disagreed. Not more than five minutes into my talk, the look of boredom on their faces was unmistakable; ten minutes in, twitching and ceiling-gazing confirmed that I had seriously miscalculated. Any doubt about the general interest level was erased by the salty character seated directly in front of me whose booming snores nearly drowned out my words.
Yet after the ordeal had finally ended, a large number of the audience came forward to ask questions and even to express their appreciation. That pretty much defines the subject of oil analysis for boaters: For many, the subject is at best of passing interest and at worst an arcane oddity. But many serious boaters consider it an interesting technology that can be a meaningful part of their maintenance regimen. If you fall into the first category, read on at your risk but please don’t snore.
The proper term for this process is spectographic oil analysis, and it’s surprisingly simple: A technician burns a representative sample of lubricating oil in the presence of a device—an emission spectrograph—that analyzes the color of the flame and determines what’s in the sample. Since every element leaves a unique spectrographic signature when it’s burned, the machine can tell with great accuracy not only what’s present but in what quantity.
The “what” here can be anything from metal to fuel to coolant. Clearly if your test comes back indicating the presence of fuel or coolant, your engine’s got a big problem. In the former case, fuel is not being burned in the combustion chamber and is seeping past piston rings into the lubricating oil, where it’s diluting it and reducing its effectiveness. In the latter case, you’ve probably either got a cracked block or a blown head gasket. Both conditions are potentially catastrophic and need immediate attention.
The presence of metals is typically a more subtle indicator. Technicians divide the metals category into those derived from additives, contaminants, and wear. Additive metals are actually part of the lubricating oil, so their presence and concentration indicates the effectiveness of the oil and whether the proper weight and grade is being used. Wear metals are derived from engine components—things like bearings, piston rings, valves, and so on. Contaminant metals are neither of the previous two but rather foreign matter that has somehow found its way into your engine, perhaps by a faulty air-intake system or leaking gasket.
The key here is that the presence of any wear metal can be traced pretty accurately to a specific engine component. For instance, oil analysis revealing the presence of lead points directly to bearing wear. Indeed, because bearings are typically made of layers of different metals, it can indicate the degree of bearing wear.
The best part: This information comes cheap. If you take your own oil sample, which is easy to do thanks to the kits supplied by most labs, you can mail it in and get comprehensive results, often along with diagnoses and suggestions for remediation, by return mail for around $30. But even if you turn the whole thing over to your mechanic or boatyard, you should end up paying no more than $100 per sample. When you consider what you’d pay a mechanic to give your engine or marine gear a diagnostic check-up, that’s a real bargain.
But there is a catch. Oil analysis does a great job of alerting you to serious mechanical maladies, but for most of us, its real value will be indicating trends: alerting us to components that are approaching the end of their lives, as opposed to having already failed. To provide this early warning you’ll need a series of readings that can indicate anomalies in wear patterns. In other words, you’ll need to send in periodic oil samplings for analysis. For the average boater this probably means every 100 hours or annually.
Although the process of taking the sample is simple, there are a few things to keep in mind, whether you do it yourself or have someone else do it. Always take a sample from a warm engine so the oil has been thoroughly circulated. Don’t take a sample right after an oil change or the addition of oil; wait at least ten engine hours. Clean the area from which you are taking the sample to avoid contamination from exterior dirt and grime. And don’t take the sample as part of an oil change, even though it’s easier and cheaper. The oil is probably at the end of its useful life. Instead take your sample roughly midway between oil changes.
If you and your boat are in it for the long haul together, oil analysis is a little expense and bother that returns big dividends—even if it’s not terribly exciting to listen to someone talk about.