I’m curious as to what people think should be the fuel to use in the 912 (ULS) and then what they actually do. I’ve been using the highest rated mogas I can find but it takes me an hour to pour 10g in the tanks. I can’t be spending more time fuelling than flying so I’m thinking of switching to 100LL. And presumably once I start cross countrys I most likely will only find avgas anyway.

so... do people shrug and use avgas with the additive, do the half interval oil changes? Only use avgas when there is no other choice? Carry mogas with you? And can you mix the two or do you have to drain the tank before switching?


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You can mix auto fuel and 100LL. You might want to get some of these:


Hi Paul,

I fuel with mogas whenever possible. Having said that, it is next impossible to find mogas when flying cross country so when I am using 100LL, I use Decalin. At the Rotax engine servicing course, they showed a torn down engine with  2000 hours that used 100LL exclusively without Decalin and one with 2000 hours of 100LL using Decalin. The engine that did not use Decalin was fouled quite badly (rings were complete seized onto the pistons) and the one using Decalin was significantly better. Having seen both of those engines, I will always use mogas whenever possible.

Regarding fueling the plane, I had the same issue fueling my plane from a ladder and jerry cans (and I am too old and feeble to lift that much weight). I don't have any electricity at my hangar but I finally sprung for a 12 volt fueling pump like farmers and contractors use on the portable tanks that they have in the back of their pickup trucks. I was also going to buy one of those 100 gallon tanks that the contractors have, but I ran across a 25 gallon steel barrel that had hydraulic fluid come it. I repurposed it and the price was right (free). I don't have a pickup truck, so I buy fuel from the gas station and haul it to the hangar in jerry cans. I then dump the fuel into the barrel using a large funnel which makes it quite easy. From there it is easy to pump the mogas up into the wing tanks. Much easier and quicker than before. Did cost some $, though.

Good luck,


Used auto gas now for 576 hours.  N316JL has never had 100LL in her.  I change the oil at 50 hours. Haven't made a really long cross country yet.



I did the same as you until I decided to build a fuel trailer.

See this post in the forum:



Mogas is preferred fuel for 912 and without ethanol is better. I have 1200 hrs on engine with lousy Calif 91 mogas with ethanol  and it runs fine.

When flying long distances where no mogas and you have to use 100LL, need to add TCP or Decalin and change oil before to partial mineral. Full synthetic won't hold LL in suspension as will mineral based oils.

I usually carry a couple of 5 gal plastic cans and find a ride to gas station but it's a pain.


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