Few companies are chasing this 7 million gallon market, principally Shell, followed by Phillips Petroleum. Trailing them is ExxonMobil, which got into aviation piston oils about two years ago. Barriers to entry are high, with a long, expensive testing and approval process that doesn’t lure many participants. Approvals don’t guarantee commercial success, either. Pilots are extremely brand-loyal, and doggedly unwilling to switch for the sake of saving a few dollars on a case of oil.

After a healthy year 2000, flying hours in 2001 had begun to trail a bit due to the economy, and restrictions on general aviation after the Sept. 11 terrorist attacks have left the market sluggish.

The fleet includes about 80 percent low-compression engines, usually smaller aircraft flown only a few hours a month by recreational and weekend pilots. The other 20 percent of the fleet are high-compression models that see much heavier use, probably logging about 85 percent of the hours in general aviation. These include small airlines making daily runs, crop dusters, couriers, planes used to inspect pipelines for signs of problems, and so on.

Engine oils for all these aircraft are governed by military specifications originally written in the 1940s and 1960s. “The specs are governed by people in the Navy, and we are very limited in changes or improvements we can make in the formulas,” explains John Brant of Phillips Petroleum. “SAE standards were written for some of these standards, but that just converted the old mil specs into SAE nomenclature; they weren’t actually updated. There are very limited amounts of additives allowed, plus restrictions on the base oil that can be used. For example, the ashless dispersant in the oil cannot be greater than 0.25 percent — essentially, the oil must be totally ashless.

“The Navy doesn’t want to relinquish control, but I’m not sure they even own that many piston engines anymore,” Brant adds.

At some point in the future, the EPA will shake things up, he suggests. Aviation gasoline still contains lead, which will be targeted for elimination. At that time, the lead lubricity will be lost, and new engine oil formulas will be needed to take up the slack.

That day isn’t here yet, although the FAA has been working on low-lead and no-lead formulas for at least four years. The pollution effects of on-highway and off-road equipment is of much greater concern to EPA now. But once that’s in shape, aviation fuel could become a target of clean-air regulations. And that could be the wake-up call for piston engine oils.