I have been using 100LL in the UL Power 350IS  and have had a leaky valve and only have 60 hrs on the motor.   Started mixing 1/3 100LL to 2/3  premium unleaded 91 octane Auto gas , in hopes that excess lead has built up on the valve and the new mix will clean the valve off.

   Is anyone burning straight 91 octane auto gas or any other  types of auto gas?   

 I have looked all over and cannot find any higher octane gas other then 100LL avgas and 105 octane race gas which is priced at 12$/gallon.

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' I'm using 92 (no ethanol) in my 260i, 175 hrs and no problems, although I did have to make a trip to eastern oregon, hot and high, to finally get my rings seated.  If I'm forced to use 100LL, usually while traveling, I add 2 1/2 0z. per 10 gallons of TCP additive.  That supposedly keeps the lead in solution and it burns thru instead of depositing.

Good luck,,,,,,,,,  Lynn   ch-701    UL-260i

Lynn, thanks for the information, pumping 100LL out of a electric pump, is much easier than using 5 gal cans of race fuel...... 

Do you know if there are different strengths or makers of TCP, the TCP/Alcor  I  f found , is to be mixed at 1oz of TCP/10gals of 100LL which is fine with me , as its costs around $14.00/OZ?

Hi Pete,  The product I use is "Decalin Runup"   fuel additive from "Aircraft Spruce".  16 Oz for about 23 bucks..   1/2 Oz. per 10 gallons..  I also built a little pump & filter unit for my DC 12V outlet.  Works great for those 5 gal. jugs  and fits into a battery box to take with me,    Maybe 2 lbs. max.

Cheers,,,,,,,,,,,,  Lynn  

I also use Decalin Runup and I've had very good results so far.  It makes a significant difference in the amount and quality of the lead deposits.  What little deposits build up are soft and flaky versus the typical concrete-like lead deposits.


Hi Pete, I'm using 93 octane auto fuel with 10% ethanol.   Only have 11.5 on the engine, but I'm going to try to avoid using 100LL if I can.  I bunker a small fuel trailer with fresh fuel in the hangar for all my planned local flying.  Not sure what I am going to do with planned cross country flights.  Good luck, and let us know how it goes with it and your engine oil cooling issue as well.  Dave

Pete any anyone else using the ULPower engine...here is  a good link for coming to learn about the UL engine.


Wow that’s not good. I am running a Rotax so this is an issue for me also. We went to the Canadian Rotax distributor (Rotech Research) and took an operation and maintenance course. One of the things we learned was how to clean the gear box at 1000 hours because when using 100LL it builds up with lead gunk deposits is important (and mandatory) to clean out. We also saw an engine that went to 2000 TBO that used 100LL exclusively. It was a mess but it did make it. You couldn’t even see the rings which were welded to the pistons. The heads and valves did not look good either. We also saw a 100LL 2000 hour engine that had used Decalin and it looked much much better. I came away with the conclusion that I will avoid 100LL whenever possible but will use Decalin when inevitably I have to use 100LL. I decided to install 4 fuel tanks so I could run mogas on longer trips. In fact, I just went to the Zenith Fly-In from here in Lethbridge. Alberta and was able to use only mogas. Peter, I flew right over Alexander on my way to Mobridge, South Dakota where they have mogas. Mexico, MO also has mogas and because of my 50 gallon capacity those were the only places I bought fuel. I hope the unleaded av fuel becomes a reality (contrary to everyone else who is running a Lycosaurus...)



Thanks, that is a great link,  interesting to find out that UL is known for having oil heating problems and I am not the first, now all I have to do is figure out the cooling solution.

I Have a older A&P helping me, and at first he was leery of  the 750/350is , now he feels it is built much tighter  and better then some certified AC engines and has a lot going for it.

 Also great to hear from everyone on what there doing to beat the lead problem , if they have to use 100LL.

Sounds like the best bet is not to use it,or carry a bottle of TCP or Decalin,since the engine was not engineered to use leaded fuel, what really got me ,was all of the problems with lead in certified a.c. engines that were designed to use lead..

Looked up accidents on the NTSB website  for the 750 and only two accidents have occurred one was serious and the other was minor, both due to fuel issues.  That is great that Matt is coming out with a service letter concerning fuel issues, since that is were the two accidents, were caused by.

 By the way both were due to OLD BAD fuel !!

If you fly down to Mexico M.  again , stop on the way down I would like to see your panel and plane. There is a grass strip right north of me.   Might even follow you down........


308 hrs on a 350iS. I've only flown the last 40.
Running 91/92, w/or w/o ethanol. Several talks with previous owner, US mx and sales reps, and several friends in the experimental world. Seems that I'm rarely even capable of meeting conditions where the higher octane matters. My prop pitch (Cato) keeps the RPM well below red line at altitudes up to about 10,000 PA. I have run 100LL on a couple cross-countries where I couldn't readily get hold of 91+. And after reading more about the severity of lead issues have had I'll make more effort to mix. Overall I've a couple little things with the engine, but it's great thus far. Really happy to be working the UL Power.

Connor:      Thanks for information, I  feel better knowing someone else has been able to get by on 91 unleaded, as that is all I can find up here. I was forwarded this link by David B. on the forum ,and found it very interesting.

UL have engineered /built a amazing power plant , after flying behind a Lycoming for 37 years &  have no regrets on climbing behind a UL /750  for the next 15...........


Do I understand you right ,that the previous owner used 91 unleaded also?

Can you tell me what your oil temp is running ,and at what rpm you cruise?

                                 Peter S


Yes the previous owner used 91.  We are by no means maxing the engine out.  I'm not an engine man, and hope to not become one.  I've emails from the US reps talking about octane content, and that 91 is being used by many folks.  After several reads, and talks with folks I've satisfied my need to dig further, and believe there's no issue operating the engine the way I am with it burning 91 octane.  You can always buy some booster if you want; I'm not using any now.  From what I understand it's only at the extreme rated top-end that the higher octane is counted on the help prevent knocking.  Because of my prop (Catto, made for the eng/bird), and the fact I'm rarely down at sea level pressure I'm just not getting the engine to it's max RPM.  If you're operating at 3300 RPM running 92+ may be more pertinent.  

The previous owner had a few oil temp issues.  He installed a slightly larger, and stronger oil cooler after the one in the kit failed him.  And on hot days in SW Nevada you'd have to watch the temp.  However I rarely see it over 200F in cruise, 220 when worked in a climb, in the summer. 

I cruise around 2650 +/-.  Close to the HP/TQ crossover.  

Connor, appreciate your replies and will sleep better after using 91 unleaded with a little booster or 1-2 gallons of race fuel for the higher altitudes .

If you can find those letters from the US reps talking about octane content and other issues on the UL, I would love to read them.

                                      Peter S


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