Rich Posted April 23, 2015 Report Share Posted April 23, 2015 Good afternoon, Today I located a Mobil station that sells 91 octane non-ethanol fuel for $3.35 PG. That's the minimum for the 100 HP 912 ULS. So here's the question. How long will it keep that octane rating in the aircraft? If it slips a little lower will it be detramental to the engine? I've been using 93 octane w/10%E so no worries about the octane rating slipping below 91. The station is 15 miles out of the way to the airport. I'd like to put 30 Gallons in the plane but have concerns about the drop in octane. Thoughts appreciated. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted April 23, 2015 Report Share Posted April 23, 2015 Good afternoon, Today I located a Mobil station that sells 91 octane non-ethanol fuel for $3.35 PG. That's the minimum for the 100 HP 912 ULS. So here's the question. How long will it keep that octane rating in the aircraft? If it slips a little lower will it be detramental to the engine. I've been using 93 octane w/10%E so no worries about the octane rating slipping below 91. The station is 15 miles out of the way to the airport. I'd like to put 30 Gallons in the plane but have concerns about the drop in octane. Thoughts appreciated. It will be fine. If 91 octane is the minimum required, then 91 is good to go. Remember there is already some margin built into that spec by Rotax. It's not like 90 octane would instantly grenade your engine. Link to comment Share on other sites More sharing options...
Tom Baker Posted April 23, 2015 Report Share Posted April 23, 2015 That is what I have been running in my airplanes since 2007. I have experienced no problems. We have a 500 gallon tank. I started out splitting with one other person, and we are now splitting it 4 ways. As a side one of the fellows splitting the fuel works at a refinery. He says the 91 octane fuel is likely higher when produced, because the refineries add some cushion on their end. Link to comment Share on other sites More sharing options...
gbigs Posted April 24, 2015 Report Share Posted April 24, 2015 Good afternoon, Today I located a Mobil station that sells 91 octane non-ethanol fuel for $3.35 PG. That's the minimum for the 100 HP 912 ULS. So here's the question. How long will it keep that octane rating in the aircraft? If it slips a little lower will it be detramental to the engine? I've been using 93 octane w/10%E so no worries about the octane rating slipping below 91. The station is 15 miles out of the way to the airport. I'd like to put 30 Gallons in the plane but have concerns about the drop in octane. Thoughts appreciated. I have been using 91E10 the entire time I have owned the FD CTLSi...over 250 hours. Link to comment Share on other sites More sharing options...
Rich Posted April 26, 2015 Author Report Share Posted April 26, 2015 Thanks for the replies-------Rich Link to comment Share on other sites More sharing options...
schurch379 Posted March 21, 2016 Report Share Posted March 21, 2016 I fly to Honolulu or some other class B, C, or D island airport about twice a month. A lot of water out there in the Pacific, and with the trip distances 150 miles or less there are enough landings every year, but not much time on the Hobbs. Because I prefer to stay dry, I attended a CPS course on Rotax and keep my little fella w/ 550hrs hangered, pampered and looked after ( working w/ a Rotax engine certified mechanic who my luck! is hangered 'next door' ). Notwithstanding; in Kona 91 oct unleaded, 0%-ethanol is unavailable; so w/ my 2007 CTLS / 912 uls I mix 92 oct unleaded w/<10% ethanol ( 50% ) with 89 oct w/ unleaded, no-ethanol ( 50% ) = 90.5 oct. So, I am conceding .5 oct for <5% eth, thinking this tradeoff is probably engine favorable, overall, if anything. That is, admittedly this is slightly below the 91 oct called for, but N992SA sure seems to run beautifully with no discernible issues ( yet... ), and after asking, everyone thought there was about 0% chance for any pre-ignition issues at this very slightly lower octane..... Btw; the new plugs I got from CPS, while designed for the 912uls, were ( at least this time ) gapped at .029, not between the recommended .023-027. Only point being is that last year we just installed them upon receipt--I don't think we checked the gapping, as those that were pulled were all at .031. Now know better.... Link to comment Share on other sites More sharing options...
gbigs Posted March 21, 2016 Report Share Posted March 21, 2016 I fly to Honolulu or some other class B, C, or D island airport about twice a month. A lot of water out there in the Pacific, and with the trip distances 150 miles or less there are enough landings every year, but not much time on the Hobbs. Because I prefer to stay dry, I attended a CPS course on Rotax and keep my little fella w/ 550hrs hangered, pampered and looked after ( working w/ a Rotax engine certified mechanic who my luck! is hangered 'next door' ). Notwithstanding; in Kona 91 oct unleaded, 0%-ethanol is unavailable; so w/ my 2007 CTLS / 912 uls I mix 92 oct unleaded w/<10% ethanol ( 50% ) with 89 oct w/ unleaded, no-ethanol ( 50% ) = 90.5 oct. So, I am conceding .5 oct for <5% eth, thinking this tradeoff is probably engine favorable, overall, if anything. That is, admittedly this is slightly below the 91 oct called for, but N992SA sure seems to run beautifully with no discernible issues ( yet... ), and after asking, everyone thought there was about 0% chance for any pre-ignition issues at this very slightly lower octane..... Btw; the new plugs I got from CPS, while designed for the 912uls, were ( at least this time ) gapped at .029, not between the recommended .023-027. Only point being is that last year we just installed them upon receipt--I don't think we checked the gapping, as those that were pulled were all at .031. Now know better.... Why play chemist? Just use 91E10....again, I have used it in my new CTLSi for hundreds of hours...never 100LL. It works perfectly. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted March 21, 2016 Report Share Posted March 21, 2016 I have to agree with Burger here. The CTLS is fine with up to 10% ethanol, and I would just run the 92 octane pump gas you have available. Sure, ethanol free is ideal, but the reduction in ethanol content you are getting is probably not worth the trouble. I'd rather have the extra detonation margin -- detonation will kill your flying fun WAY faster than ethanol ever could! I have been running 93 octane pump gas (my testing shows 5-7% ethanol) since I got my CTSW three years ago. I have never found any water in my fuel, had any vapor lock issues, noticed any fuel system damage, or had any other type of problem. I have had no problem taking very long cross countries, and I only use 100LL when I can't get pump gas. Some things you really have to be diligent about with the CTs...I don't think ethanol in fuel in such an item. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 21, 2016 Report Share Posted March 21, 2016 Really bad idea and plying with fire. I'm sitting at this very moment in a Rotax class with Eric Tucker and Ronnie Smith. You need to stop before you have an issue. The only accepted fuel mix is 89 oct. with a 50% mix of 100LL which gives the minimum 91 oct. Nothing less on the the percentage when using 89 oct. you would need so much 92 oct. to raise the 89 oct 2 points it is an act in futility. You are headed for a detonation problem one day and it will cost thousands of dollars. Run the ethanol fuel. It will not hurt anything nor absorb water or moisture like you think. The plug gaps should be set for the .023 - .027 gap. Not wider as it runs too cool and it causes poor spark and flame burn. Just use your 92 oct (best idea) or a 50/50% mix of 89 with 100LL. Link to comment Share on other sites More sharing options...
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