Scientific Method Page 2
Analyzing oil is as high-tech a process as any used by those CSI labs. Thompson Tractor’s lab in Tarrant, Alabama, employs something called an Inductively Coupled Plasma Mass Spectrometry (ICP) unit manufactured by PerkinElmer, the company that collaborated with Lockheed Aerospace to build the Hubble telescope. The customer sends the oil sample to the lab with a detailed description including: the oil’s viscosity rating, brand, and hours in use; the engine manufacturer, engine serial number, and hours—both total hours and since the last oil change; and the client’s contact information. As the oil is burned in the ICP unit, the ICP automatically analyzes the wavelength of the light in the resulting flame; each spectrum segment represents a specific element—aluminum, chromium, iron, nickel, etc.—and the machine can compute the amounts of each in parts per million (ppm). The machine is so sensitive, Sewell tells me, that if I were to drop a penny in the sample before sending it to the lab, it would detect a minute increase in copper.
The ICP unit detects and measures the presence of most elements, but for those such as water, antifreeze, and fuel, Thompson’s uses a Fourier Transform Infrared Analysis (FT-IR) to identify problems not related to wear. “[Many] of the contaminates in your engine come from the fuel you burn and the air intake,” says Sewell, who points out that they lower the oil’s lubricating ability. The FT-IR uses a complicated process involving lasers; all you need to know is the results are reported in centiliters per milliliter and compared against a baseline, and the summary that comes with the test will tell you that.
Whether you’re a boat owner or a boat buyer, spectrographic oil analysis and FT-IR testing provides the kind of detailed information forecasting potential problems that you just can’t get anywhere else. It basically removes the guesswork for analyzing the health of your engines. It sort of reminds me of when my life-insurance company ordered a bunch of blood work before they’d approve my policy. Consider spectrographic analysis as blood work on your engine’s lifeblood; it may be the most revealing indicator regarding the health of your engines.
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Before PMY senior editor Capt. Bill Pike purchased his 32-foot Grand Banks Betty Jane, he had an oil analysis done on her 135-hp Ford Lehman diesel inboard. The results showed that wear and contaminate levels were normal. To see how her powerplant has fared 287 engine hours later, we had Sewell draw a sample to be sent to Thompson Tractor's lab, and we drew another one that we mailed to Ohio-based AV Lubricants.
Drawing the sample is simple: we used an aluminum oil pump that sucks oil directly from the engine via a tube that is placed deep inside the dipstick hole. Pulling back on the plunger draws oil directly into the sample bottle that is threaded to the other side of the pump’s exhaust port, ensuring a good seal and virtually no mess. Sewell emphasized the importance of avoiding contamination of the sample, especially from the engine exterior, dirty rags, and soiled hands.
We received the results from both outfits within 72 hours—both agreed that element levels were normal. When I spoke to technicians from both labs, they emphasized that generally, trends are more important than absolute levels. A spike in the concentration of any element should be cause for concern. Betty Jane’s Lehman has aluminum in its pistons, copper as part of its rod and cam bearings, iron in its block and camshaft, and chromium in its piston rings, all of which had single-digit concentrations, a good sign. Potassium concentrations were also in the single digits. High numbers (more than 50 ppm) might indicate coolant contamination from a bad gasket. Regardless of the baseline, most technicians flag a sample if the potassium and sodium numbers exceed 150 ppm, as this can mean a cracked cylinder head.
But low numbers aren’t always a good thing. Nonsynthetic oil contains phosphorus as an antiwear additive, so a number around 1,000 ppm is normal, and one less than 200 ppm is a concern that the oil needs to be changed more frequently. Zinc (1,300 ppm average), calcium (2,325 ppm), and magnesium (118 ppm) comprise the oil’s detergent package, which keeps contaminants suspended so they are drained with the oil during an oil change. Low readings indicate the presence of excessive contaminant and the need for more frequent oil changes or perhaps a change to different oil.
Water, antifreeze, fuel, soot, and viscosity all appeared normal in our sample. Concentrations of one to four percent by volume are considered normal, and a sample wouldn’t fail until it hit 7.5 percent. While I could not obtain a pass/fail number on soot contamination, I was able to find out that, depending on the viscosity grade, most oils average between 14.5 and 15.1 centistokes at 100 degrees Celsius, or normal running temperature.
Remember that your results will vary. These numbers are only for the engine we tested.
This article originally appeared in the April 2007 issue of Power & Motoryacht magazine.