Whadayamean Unleaded Fuel Will Trash My Valves?



Now that GAMI’s G100UL is fully approved and awaiting distribution, owners are hearing questions about how unleaded fuel might cause valve damage in aircraft engines. It was once a thing in car engines, but in this video, AVweb’s Paul Bertorelli examines the issues and finds valve seat recession an unlikely consequence of using unleaded aviation fuel.

Addition AVweb videos on unleaded fuel

The Long, Twisted and Slightly Ridiculous Story of Avgas Part 1
https://www.youtube.com/watch?v=9F-WngVMJBQ&t

The Long, Twisted and Slightly Ridiculous Story of Avgas Part 2
https://www.youtube.com/watch?v=Mvse4Xhzwuk&t=1s

G100UL Approval
https://www.youtube.com/watch?v=ibIkuyBL9i8

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20 thoughts on “Whadayamean Unleaded Fuel Will Trash My Valves?”

  1. Lead is extremely corrosive when an engine is stored. I've seen dozens of C Continental jugs with pistons and numerous things can attack them, but not a lack of lead. There's one more aspect to unleaded plane gas. Politeness. You can drop in, buy a Tee shirt and a hot dog, and gas up with no second thought. If your tank is 100% no lead, it's fine to drain all your plane gas into your car. I can't wait until lead is gone, altogether.

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  2. Cars had an identical problem with this in the 70s. We have non-toxic lead substitutes nowadays to solve this problem for those who don't want to retrofit hardened valve seats into their engines

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  3. I've never flown in a small plane, I never expect to, much less own and need to fuel or maintain one, but I still watched through the entire video. Great job presenting the information well enough even a complete layperson can find it interesting! Praise The Algorithm!

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  4. God I'm sick of generalisations … even by experts. Noone can generalise about any fuel in any car. There's only one real answer: Every valve and every valve seat and every combustion chamber is made to the manufacturer's specifications for each particular engine model to be most efficient and ling lasting with a particular fuel. If you want to know the true answer for YOUR ENGINE, ask the manufacturer. Any fuel outside of their design and production parameters is an engine degrader in some way in some time frame.

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  5. An interesting comparison is the larger capacity air cooled Volkswagen engines (1585cc Type 1 and the pancake / suitcase 1970cc Type 4 Varient derived Transporter engines). These were rated to run on RON 90/91 fuel. The Californian specification engines may be of interest because of the mandatory use of catalytic converters which mandates the use of unleaded fuel.

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  6. For years and years Amaco had lead free gasoline. Long befor other brands went lead free. It had an octane of 95. My Dad use to run it in his vehicles for years. Also in the lawn mower, motorcycles, or any engine. Instead of lead they were using a chemical called “ Nichol- molibdium” to lubricate the valves. I may have spelled that wrong. It never went stale when stored. Or turned to gum. And the high octane never pitted the pistons of small engines. It was also great in 2 cycle engines. It was a great fuel. But in time went all others went lead free they changed the formula in Amaco gas. It’s not the same fuel anymore. And I believe all lead free gas is the same except for the added cleaning agents. Aviation fuel has extra components added to prevent boiling at higher altitudes. I have found that for automotive fuel EXON has the best cleaning agents to prevent carbon build up under the valves. The Ford eco boost engines are prone to carbon build up due to the way the emission system works.

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