How long is too long for oil change intervals? Ed Kollin, the creator of the oil additive CamGuard and an early researcher for the Exxon Elite oil blend, believes too many operators are stretching oil changes beyond the capabilities of even the best aviation oil. If you only fly between 25 and 100 hours per year, you could be in that camp. As a result, ASL CamGuard has been flight testing a new oil that might safely double oil change intervals. First, some background.
I dusted off several aircraft operating manuals on the bookshelf and found that some manufacturers suggest changing dispersant engine oil at 100 hours. Forget that—those manuals were written in the Reagan era. Aircraft engine manufacturers have since standardized the oil change interval to 50 hours on engines with spin-on oil filters and 25 hours on engines with filter screens. According to Kollin, he has done enough engine wear analysis to suggest there is zero scientific basis in these recommendations, with plenty of trashed cams, rings, spawled lifters and other toasted engine components as evidence. Where’s the smoking gun? There are several.
Think beyond oil filter technology because even the most modern filters simply can’t filter out water, acid and blow-by gasses. Blow-by is a smorgasbord of raw and partially burned aviation fuel, carbon dioxide and tiny lead particles that sneak past ring seals, eventually forming damaging sludge and deposits in the engine. Consider that the majority of wear on the surface of lifters and cams comes from abrasive particles (ingested dirt, sand and silicon dioxide, for example) in the 10-micron range—far smaller than the 60-micron filtering capabilities of a paper oil filter.
As for oil longevity, the key is dumping it before it can no longer suspend the oxidized blow-by fuel that, according to Kollin, “causes virtually all oil-related problems” we’re seeing with typical air-cooled aircraft engines. Kollin stresses that preventing the deposit-forming liquid fuel component and other contaminants in fuel blow-by is just as important as preventing corrosion. Ten-hour oil, he says, is already corrosive due to water contaminated with salts and acids, and is partly the basis behind the corrosion- and sludge-inhibiting CamGuard oil additive product, which has been shown to repel water and acidic molecules by filming on the surface of engine metals at shutdown.
In trying to determine how often you need to pull the drain plug, Kollin developed an algorithm that considers a slew of factors, including rich of peak and lean of peak engine operation, the size and horsepower of the engine, climate characteristics, normal cruise oil temperature and other operational variables. When he hit the Go button, he came up with oil change intervals from 25 to 35 hours—the period in which the dispersant in the typical aviation oil is used up, and when the damage begins.
Tentatively named Advantage, the new 25W50 oil (25W60 for radial engines) would contain the right amount of additives to safely extend oil change intervals to 45-50 hours. Without revealing his secret sauce, Kollin said that Advantage will of course consist partly of the CamGuard additive. “The goal is to have the Advantage (at 50 hours) chemically look like a Phillips/CamGuard mixture does now at 25 hours,” he told me. Kollin was realistic in admitting he’s not sure if the oil can make 50 hours, but field testing—which is currently underway—will tell. He also admitted the oil would cost a bit more, but I think the delta could be made up in longer change intervals. We’ll keep tabs on Advantage’s development and look at oil additives in an upcoming issue of Aviation Consumer.
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