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Rotax auto fuel

Doubting Tomas!

It says 91 octane on the pump sticker on the pump where I buy my fuel to. I guess its a leap of faith but seems to run fine in my plane. Ive used about 200 gallons so far. :eek:Here is a web site created for ethanol free fuel. I buy fuel from Enderbys in Gainesville Texas as shown on the web site.
http://www.pure-gas.org/station?station_id=5294
 
Marathon Premium

The Marathon Premium I buy about 5 miles from I19 says 93 Octane on the pump. Doesn't mention ethanol content. If I use the simple test (drops of blue fluid) it ALL goes to the bottom, indicating 0 ethanol. If I use the water test (EAA test kit comes with directions for both) it indicates about 5% or a little less. So far I haven''t seen any symptoms of vapor lock (last Saturday the OAT on the ramp, prop turning, was 100F, I didn't think (or sit under the bubble) to wait for a reading after shutting down). I guess, as Sfcott says, that's why that electric pump is back there pushing fuel.

Wayne 120241/143WM
 
dick seiders said:
John, are you certain the fuel you reference is 91, not 90? If it is 91 who makes it?
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Premium unleaded auto gas in all states is defined as 91 AKI or above. I know of no state that has a 90 AKI premium unleaded auto fuel. That would be classified as mid-grade. It turns out that 90 AKI "recreational fuel" is NOT premium unleaded auto fuel and is intended for off road use. Marathon Oil sells 90 AKI "recreational fuel" in a lot of states and it is primarily intended for use in the marine environment as ethanol spreads into all of the gasoline for cars. Marathon is very adamant that none of their auto fuels is intended for use in aviation. I have heard rumors that there are other suppliers bringing out 90 AKI "recreational fuel" for off road use, as ethanol spreads everywhere.

Any 90 AKI "recreational fuel" would NOT be approved for use in a Rotax 912 or any Petersen high compression STC, although it could be used in the 85 HP Rotax which allows the use of 87 AKI auto fuel as do the EAA STCs and the Peterson low compression STCs.

It turns out that 90 AKI fuel could also be the base blendstock for making premium unleaded E10 for these companies as ethanol will raise the AKI level by about 3 points, however blendstock for oxygenated blending (BOB) is usually NOT legal fuel for commercial sale because it has some other tweaks for making E10 optimally.
 
I wonder!

I believe this may have been discussed already, but can't find it, sorry. Madison Airport (52A) only 19 mi. from my home base (9A1) has installed a tank and is going to start selling car gas that is rated for aircraft. It is (guarenteed) 90 octane with NO ethanol, and is called Recreational Aviation Fuel.
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Dick from what Dean just said doesn't it make you wonder where the fuel is coming from for 52A being 90 Octane.:confused:
 
John, as far as I know it is from Marathon, but I am trying to get tha confirmed by Madison. Will post as soon as I can determine.

Dick seiders
 
Just as a follow up on what we started talking about a few weeks ago, the annual will be done on New Blue tomorrow. As far as the lead goes, as expected, there was some that had settled to the bottom of the oil tank. Actually, there was so little I couldn't get a good picture showing it. But please keep in mind, we remove and clean the tank at every oil change plus we purge the engine every time as well. So you really shouldn't expect much.

The carbs were disassembled, cleaned with gaskets, o-rings, etc. replaced. There was only the slighest hint of blue anywhere.

We'll be reinstalling and balancing the carbs tomorrow. If there is anything to report, I will.
 
I still haven't heard anything from the Madison Airport people, so until I have more facts from them I am taking the position that 90 octane Recreational fuel is not suitable for the 912uls. This based on discussion with Lockwood tech. assistance, which refers to Rotax SI 912-016-R4 for the requirements. The SI clearly states that 91AKI is the minimum octane. AKI is the result of the RON, and MON rating for the fuel divided by 2. (R+M/2). If the mogas pump is labeled 91-93 octane it has a min AKI of 91, and as such is suitable. If the octane rating is less than 91 it is not. The ethanol content is discussed only to confirm that up to 10% is acceptable.
Now I know that most of the 12 drivers know this so I am merely confirming the requirements as posted in the SI. I will continue to try to nail down the source of the 90 octane at 52A.
I think it's safe to say one can use whatever fuel one chooses, but using octane below 91 likely will cause pre-ignition/detonation damage to the 912uls.
Dick Seiders
 
Getting back to this thread you all may be interested to hear that Madison GA airport is STILL not selling the 90 octane ethanol free fuel mentioned earlier.
That fuel IS being provided however, at the Monroe GA airport, and it specifically states it is 90 aki. I have been advised by one of my flying friends that he is using it in a 912uls. He is now going to switch to a Valero supplied 90 aki ethanol free fuel as it is closer to his location than Monroe.. I checked the Valero station located near Loganville GA and that is what they are selling. They specifically said it is NOT 91 aki. My friend will keep me posted on his experiences using this fuel as time goes by and I will post it here when available. Any other news out there on this old topic?
Dick Seiders
 
Hi Dick,

The issue that may come up with only 90 oct. is there are several factors both in our control and some out of our control that may decrease that number down to 89 or worse at any given moment. So your friend is rolling the dice with an $18K engine. The octane is to help prevent detonation. Give a slight variance someday in conditions and the detonation will happen so fast it will be over before he even knows it happened. That fix depending if it is one cyl. or more will start at around $4500. Looking back after the fact and you would have to ask yourself if the gamble was worth it? The higher octane is there for detonation avoidance not better performance.

If the engine is under warranty this would void the warranty.

Who knows he may get away with it for a year or much longer or just until next week.
 
FWIW, This is what I do

I burn 90 octane zero ethanol about 70% of the time. I add octane boost to the fuel to get it to at least 91 octane, which is the minimum recommended by Rotax. In the Midwest, it's about all you can get.

When flying cross country, I will divert to get auto fuel if it's available but I'm okay with burning 100 LL if nothing else is available. I always add Decalin to the fuel to help scavage the lead out of the engine. I burn this about 30% of the time. When I do, I change the oil more often because I can see the difference in the oil when burning 100 LL.

Currently, I'm burning Shell 93 octane V-Power with up to 10% ethanol. I have a tester and I've never found the ethanol at 10%. It's usually around 7%. I've grown a little tired of all the mixing of additives so I'm thinking of just going to premium auto fuel from this point forward.

Bottom line is that I always carry a bottle of octane boost, a can of Decalin, and an ethanol tester with me at all times. I bought a water-tight case from The Container Store that I carry in the baggage area.

What I get from the material on the Rotax owners site is that it's okay to burn E10 in the Rotax. In fact, it's preferable to burning 100LL. Lead is bad for the gearbox and valve guides so if you can avoid it, you should. By the same token, you shouldn't be paranoid about burning it if it's all you can find. Just use a lead scavenger. Another pilot on my field burns a mixture of 90 octane E0 and 100LL, obstensively to get the octane rating up. To me, it's the worst of both worlds and I had no interest of going down this path.

This is what I do and I'm comfortable with my decisions up to this point.
 
Everyone I personally know with a 912 uses auto fuel with ethanol and has never looked back. I have used it for close to 12-15 years. We have tested ours in AZ and found it is usually 6-7%. We have never seen 8-10%. Fuel pumps usually say up to 10%.
 
All I can say is be careful. I have sources of 92 Oct non-ethanol fuel and have used nothing but, since I brought by RV-12 back from Oklahoma. However, I did get some fuel, represented as non-ethanol, that had ethanol and was contaminated with water. It first showed up when I sumped the fuel drain. I then sumped a pint -- which showed clear, put it in the freezer for an hour and observed phase separation of alcohol and water in the fuel. So, if you have water absorbed into the alcohol in your fuel, it's possible to have phase separation occur when the temperature drops below the saturation point.
 
I prefer to go blissfully ignorant into the wild blue yonder careless of such dragons waiting to smite me --- so far, so good! :D
 
I agree with all who are using autogas 91-93 octane as I have since new with exception of my flight to Oshkosh 2 yrs ago when I had to use 100ll. I am intrigued tho by finding an ethanol free 91 aki as ethanol is a solvent and not real helpful to the Rotax and it's hose system so I will continue to use what I have been while investigating a better alternative. I have had no phase out issues producing water separation in the four years and 230 flying hrs in that period. I also never have not refilled my tank at least once in a 30 day period.

My flying buddy using the 90 aki ethanol free autogas advised me yesterday that he has been using it now for two years, but has only flown 50-60 hrs in that time frame. There have been no adverse effects thus far. I will continue to ask him for feedback on future experience as it unfolds.
Dick Seiders
 
Hi Dick,

The guy using the 90 octane could get away with this for years and many hours. The problem is you never know when the "perfect storm" forms to cause a problem.
 
The ethanol won't hurt the engine or the fuel hoses. If ethanol ate fuel hose all the time all our cars would be sitting on the side of the road.
 
You're probably right Roger, but the ethanol sure hammers the hoses on my mowers, blowers and trimmers. Besides why do you suppose Rotax requires a hose change out every five years????
Dick Seiders
 
dick seiders said:
You're probably right Roger, but the ethanol sure hammers the hoses on my mowers, blowers and trimmers. Besides why do you suppose Rotax requires a hose change out every five years????
Dick Seiders
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Dick,
Are you saying ethanol is the reason that Rotax calls for a five year hose change? That is the first I've heard of that reason for this procedure. Do you have a specific reference or are you speculating?
My mowers run on 10% ethanol all the time and have no problems with fuel system components of any kind. There is seldom anything but anecdotal evidence of ethanol damage to any systems designed and built in the last couple of decades. Are the manufacturers of your equipment restricting ethanol use?
Any fuel has conditions in which it can cause detrimental effects. Car gas goes skunky and releases varnish if you let it sit long enough. I have used it 9 months old and not had a problem and I've had a lawn mower I let sit with it for a year and I had to clean out the carb. Different seasonal and regional blends make one somewhat unsure of what you are getting for car gas. I run 91 octane year round in my Rotax and have no problems. I fly 100 or more hours a year at regular intervals so my gas doesn't sit all that long before it's refreshed. And 100LL? That stuff is god awful for engines. Again, since the 70's or so, most engines have hardened valve seats and don't need lead for lubrication. My point is that each fuel has advantages and disadvantages and each probably has it's place in the scheme of things. One has to use them appropriately. I have a Champ with an auto gas STC that does not permit ethanol. I burn car gas in it but not ethanol as I imagine all the hoses and fittings in it are "pre-ethanol" days and they may be broken down. The new stuff? I go with what the manufacturer says.
 
Agree

Agree. It is a "rubber gets old, hot, hard an brittle" issue..not an ethanol issue. Rubber in any engine compartment will deteriorate...usually from the inside out. The Rotax 5-year recommendation includes the coolant hoses which never see any fuel. Even the automobile industry recommends replacing rubber engine compartment pieces at regular intervals to prevent your car from breaking down. Since we can't really afford a "break-down," this might be a good rule of thumb to follow up on. The bigger question to me is what to replace it with - all rubber is not equal.
 
Hi Dick,

Most of today's fuel hose can handle ethanol and I do believe some probably better than others. Rotax requires the 5 year rubber change not because of ethanol, but because hose MFG's have shown a large spike in hose failures in this area. Gates shows a huge failure rate spike at 4 years. Like you said we can't just pull over and I'm afraid I might be flying over the Grand Canyon and that isn't my first choice of places to have an engine shutdown.
Rubber ages even without all the other factors being thrown at it. Ozone alone will help shorten its life.

The hole idea is better safe than sorry. Can hose last longer, sure, but why throw the dice all the time.
 
When does the clock start ticking on the 5 year replacement. Time of hose manufacture? First engine start? ...?
 
My last assignment prior to retirement from the nuclear utility industry was operating license renewal and aging management programs. Rubber and elastomers were a broad category we worried about. We supplemented routine replacement with visual inspections for cracking and the squeeze test to identify loss of elasticity.
 
Many Rotax engines are put in service within a few months from MFG. Some of course may be on someone's bench for 2-3 years. Those years count against you. So for the majority of us I would say when you buy the engine or aircraft as new whether on a plane ready to fly or in the crate that is the start time. Rotax actually says if the engine hasn't been started from the date of MFG for 2 years they want all the "O" rings replaced. That is expensive.

I do about 12+ rubber replacements a year. You can't see under fire sleeve to inspect hose, squeezing is worthless unless the hose is so old it's getting hard which depends on several factors. Things like leaving it outside or in the sun a lot and many use the wrong types of hose. I find most of my bad hoses with the damage on the inside especially around the fittings. I see lots of cracking on the outside of the fittings. Some mechanically damaged from over clamping, the wrong types of clamps and no abrasion protection when needed.
 
Hmm, thanks Roger. Might be a few builders out there with a bit less time to run to first major expense than anticipated, me included.
 
Robert - have you decided what to save up for? Should we be replacing with the same 5 year pieces or should we consider something else. For example, should we be considering conductive teflon hoses instead? The claim of course is no more replacements. Don't know anything about conductive teflon.
 
I don't know Pete, but I still have close to 3 years to go before I need to decide. By then Aircraft Specialty's hose package should have been given a good run, and I'd be tempted to use that if the reports are good. However, I'm still close to the bottom of the learning curve when it comes to the engine. Unfortunately we don't have the level of access to Rotax courses and support that you guys in the US do. Roger's comment about the O-rings is a concern too. I'm just a week or two off first engine start, but I'd hate to have possible warranty issues because there was a note somewhere in the Rotax fine print that I didn't see.
 
All responders,
I am not speculating that Rotax hoses are impacted by ethanol, but I am confident that the stuff is not a hose life extender after doing the rubber hoses on the other equipment I mentioned. Rotax says change all the hoses at 5 yrs so that is what I will do. However, I don't buy into the statement that an unmounted new engine has the same hose/o ring wear rate as one that is being operated on a regular basis. I mean does the clock start as the hose comes out of a mfg device? I kind of doubt that, but I will follow the 5 yr deal as that is recommended by the mfr. That other more extreme view of start time is more CYA than anything else.
As stated earlier I will keep you posted on the 90aki ethanol free guy as the info becomes available. I appreciate all the comments and feel a fuel thread does more good than harm.
Dick Seiders
 
Environment plays a role too. The summer temperature here in AZ probably makes it more risky to go beyond 5 years than operations in more temperate areas. Can't prove it, but temperature is known to accelerate aging in elastomers.
 
RFSchaller is absolutely right. Time alone ages hose not to mention the elements in the air. Hose doesn't have to be in service to age. Then depending on the type of service hose can age at faster or slower rates. Many companies have published hose service time intervals.
 
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