Continental sends mixed messages on unleaded fuels

Teledyne Continental Motors has done a number of tests with unleaded gasoline that is supposed to be made to the ASTM spec for 94 UL avgas.

There have been several PR releases about these tests, including a report at

Apparently the tests are a complete success and Continental is ready to certify all of its engines for the new unleaded avgas.

The funny thing is that Continental also says on its website not to use unleaded gasoline in its engines.

Officials make it very clear that Continental engines must have TEL in the gasoline:

“Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours.”

I guess none of their tests were longer than 10 hours. Either that or Continental has been publishing propaganda to keep users from using unleaded auto fuel, “mogas,” in its engines. Considering the other warnings, that appears to be the case.

Such statements as: “It is important to note that automotive gasolines are not subject to the high level of quality control applied to avgas. The allowable concentrations of additives, contaminants, and water in avgas are precisely controlled by ASTM D910. Automotive gasolines within the United States are changing rapidly to meet ever more demanding environmental regulations” are pretty ironic, considering that it is the more “demanding environmental regulations” that are ending the use of TEL in avgas, and the idea that unleaded auto fuel has ” …contaminants and water …” in it is absurd.

No refinery in the U.S. would deliberately allow contaminants and water in refined auto fuel any more than they would allow it in avgas.  Modern fuel-injected cars and pollution systems require clean, tightly controlled fuel specifications.  All brand-name gasoline is filtered for contaminates and water throughout the entire distribution and delivery process.  Ethanol-free gasoline, which is the only gasoline allowed on an airport since it is a recognized aviation gasoline by the FAA-approved STC process, would not absorb any more water than 100LL avgas and the pumps would have water filters just like the pumps for avgas in case there was water in the storage tank.

“Some states do not even require that automotive gasoline conform to the ASTM D4814 industry standard.” I would like Continental to identify one state that doesn’t require unleaded auto fuel to meet ASTM D4814 in this day and age of auto warranties and EPA requirements. Even if the statement is true, mogas delivered to an airport would meet ASTM D4814.  It would be specified in the order just as gasoline meeting ASTM D910 is specified in any order for avgas. No FBO places an order for avgas, or mogas, without the ASTM specification in the order.  To say that “Alcohol content of auto fuels may also result in damage to o-rings, seals, and other elastomer components in the fuel system” is a smokescreen. No unleaded gasoline ordered by an FBO on an airport would contain ethanol.  There are no Type Certificated aircraft with a mogas STC that allows for unleaded gasoline with ethanol in it.

I wonder when Continental is going to change its website?

Contributed by Dean Billing

The GAfuels Blog is written by three private pilots concerned about the future availability of fuels for piston-engine aircraft. They are:

  • Dean Billing (Sisters, Ore.) – an expert on autogas and ethanol
  • Kent Misegades (Cary, N.C.) – an aerospace engineer and aviation journalist
  • Todd Petersen (Minden, Neb.) – former aerial applicator and owner of more than 150 Mogas STCs for aircraft

For a list of airports that have ethanol-free fuel and those no longer pumping it, compiled by the authors, follow this link.


  1. says

    Nice was really knowledgeable and also interesting..I do believe that the future of fuel is water and hydrogen..which are easily available and also environment friendly..keep posting I will wait for some more like this.

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