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Permalink Reply by John Austin on September 28, 2026 at 11:48am

In my previous late Gen 2 and my Gen 4, I have always run 93 AKI no ethanol auto gas and only used 100LL on cross-countries where I couldn't get mogas.  Jabiru specifies 95 RON auto gas which is about 90-91 AKI gas in the USA.  Mid-grade in my area is only 89 AKI, so I use the 93 and figure is better to be a little above what is minimally necessary.  Also, an interesting factoid is that the higher the octane, the slower that auto gas degrades in storage. (I have a tanker trailer and typically buy about 6-9 months of fuel at a time,  I also add PRI-G fuel stabilizer as a precaution.)

Given all this, I have had zero problems with auto gas plus it usually is about $1/gal cheaper than 100LL.  I think the biggest plus is that your engine will run much cleaner with less cylinder deposits and cleaner plugs.  I do not use auto gas with ethanol as it is hygroscopic.

John

N750A

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Permalink Reply by Bobby Egger on September 29, 2026 at 8:30am

Thank you for the reply. I think i will try a couple of tanks and see what happens. 100LL just jumped to $6.55 gallon by me. 

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Permalink Reply by John Burns on September 29, 2026 at 8:24am

I consistently run ethanol free 90 octane autogas in my Gen 4 Jabiru.  No problems so far.  I did run 100LL during the 40-hour test period and I run 100LL when it is all I can find on cross country flights.  I do borescope inspections every year and you can see 100LL deposits on the intake valve stems.  I now try to run Decalin in the fuel when I have to use 100LL.

This has worked for me for 250 hours of flight time.  As they say your experience may vary.

For sources of ethanol free gas see Pure-gas.org - ethanol-free gasoline in the U.S. and Canada

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Permalink Reply by Bobby Egger on September 29, 2026 at 8:43am

Thank you for the reply. I am going to run a couple tank through and see how it does. 

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