Black Gold, Texas Tea, or dinosaur juice, no matter what you call it, oil is truly the lifeblood of every piston engine. It cools, it lubricates, and it cleans. We all agree on that. But what everybody disagrees about is which oil is best?

The experts at ExxonMobil (www.exxonelite.com) have tackled this issue by sponsoring an in-depth study of piston aircraft engines to determine, statistically anyway, how well their Exxon Aviation Oil Elite protects engines. To make sure there could be no claims of bias, ExxonMobil hired CTC Analytical Services, an independent oil analysis company, to do all the analysis and data collection for the project.

The data was collected from samples that had been analyzed over a period covering about five years, according to Steve Sunseri, ExxonMobil’s general aviation manager. He added that ExxonMobil and CTC were extremely careful about which samples were used in the statistical findings. “For the purpose of the analysis, we didn’t select engines, we didn’t select aircraft, we didn’t select oil types,” he explained. “Instead, we took everything that we had from the database and then we made sure there was no bias related to the engine type.

“For example, if you had the engine they put in the Diamond DA20, which actually produces not a lot of wear materials, if you had a lot of those engines in there, it would bias the analysis figures,” Sunseri said. “You can imagine that we had to be ready to defend our results when we presented them. We did a lot of cross-checking to make sure we were very, very confident and could stand behind the analysis we produced.”

In its brand comparison, CTC Analytical Services measured the oil in parts per million (ppm) per flight hour for aluminum, iron, copper, and chromium, all of which are indicators of engine wear. Analysis recorded wear-metal measurements for Exxon Elite, a commercial SAE 50 AD (ashless dispersant) monograde with Lycoming LW-16702 additive, a commercial 15W-50 multigrade, and a competitive mineral 20W-50.

So what did the analysis show? After looking at good data from hundreds of engines lubricated with Exxon Aviation Oil Elite 20W-50, the CTC analysts found that these engines had, on average, 33 to 50 percent less wear metals in their used oil when compared to the engines protected with competitive products. For example, Exxon Elite had 0.46 ppm compared to 1.14 for commercial AD monograde with the Lycoming additive and 2.51 ppm for the competitive mineral 20W-50.

It literally took the sampling of thousands of engines to come up with the numbers required to achieve the statistical sampling required. “Believe it or not, a lot of owners don’t really know what kind of oil is in their engines and it shows up on their oil analysis forms,” Sunseri said. “They may say they use AeroShell W80 in their engine, but when you look at the analysis results, the viscosity of the sample they submitted clearly isn’t an 80.”

So the analysts were faced with first analyzing each sample to verify what type of oil it was, then analyzing those that fit the parameters, then cross-checking those findings to make sure there was nothing that would bias the results. They also took into consideration the numbers of flight hours on the samples. It was a time-consuming process.

Achieving 33 to 50 percent less wear metals is a significant improvement in an oil’s engine-protection capabilities, so the question is: What makes Exxon Elite better? “I can’t disclose the actual formulation because it’s proprietary,” Sunseri explained. “But it’s not like we patented a magic formula that we put in here. The truth of the matter is, the product was about 10 or 15 years newer than the next nearest competitor when it was formulated.”

“We had better additives to choose from,” he continued. “I would say that we achieved these results, in addition to superior rust protection, simply because we have a newer, higher-tech formula than the competition.”

Sunseri also said that the performance of the ExxonMobil Elite brand continually surprises even the company’s own technicians. “ExxonMobil Research and Engineering, for example, didn’t think this type of research would yield results that we could hang our hats on. But they were wrong,” he added. “We are all happy that we could find a new way to actually look at real-world metal wear analysis.” And, maybe helping all of us find a way to answer the question; “Which oil is best?”