What is your experience using automotive gas in airplanes?

I fly a 601XL with a Jabiru 3300 engine. The other day I ran into an old-time pilot who has been using automotive gas in his airplane for many years. He reports no problems, in fact he had only good things to say – like longer engine life since he switched. Jabiru does permit the use of premium auto gas in the 3300. I am contemplating the switch for the following reasons:

1) Longer sparkplug life. I have gotten 170 hours out of my last two sets of spark plugs which is hours 70 more then Jabiru calls for. Last time I changed them I installed iridium plugs which I expect to last the life of the engine – unless they get too fouled up with lead to work that is. The last plugs I pulled had very significant lead deposits on them.
2) Reduced air pollution. The engine does not need the lead. Why spew it into the air then?
3) Less muck on the bottom of the plane? Even though I have exhaust pipe extenders, the underside of the airplane is impossible to keep clean. I suspect most of this is not lead but still, when I am under there on my creeper scrubbing the stuff off I wonder what is in the goo that runs down my arms.
4) Reduced cost. My plane has about 430 hours on it. If I had been burning auto gas instead of 100LL I would have saved about $4,000 dollars on fuel over the past 2 years – wow that’s not small change.

On the down side hauling up to 30 gallons of auto fuel to the airport in my car seems like a pain and possible safety issue. I have been contemplating using existing gas tank in my car for transport and use a purpose-built 12 volt electric fuel transfer pump to move the fuel – I see them on-line for about $140. I don’t tend to land my plane with the tanks completely empty – I hear it’s a bad idea – so chances are my car’s tank would almost have the fuel I need to fill the plane.

On cross countries I would revert to using 100 LL since automotive gas at airports is hard to find.

I would love to hear from those who use auto gas in their planes to learn your experiences and tricks to make this as painless as possible.

Thanks, Steve

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Comment by Jonathan Porter on April 24, 2009 at 1:06pm
OK, so I have had to stop flying due to a BIG tropical storm (just got hangared before getting floded up in 120km winds) and the internet is working so I am replying a bit late on this one...

Following on from Sebs 'refer to the engine manufacturers recommendations' let me ramble a bit!

In my opinion - and climate (tropical) if you can avoid anything other than 100LL in the Jab. Period. The dsing is such that valve seats like the lead and the compression needs the higher octane! I have flown 100 hours test on a Jab and learnt a lot.


The Rotax prefers unleaded auto/mo gas - of a good quality (see the latest MON/RON/AKI recommendations from Rotax. But if running 100LL you will have lead deposit challenges - just be aware and change the service interval (if you can use unleaded and enjoy the better service intervals.

We fly our Rotaxs ONLY on automotive fuel - 91/95 RON on the 80hp. The 100HP must have the better quality - at the end of the day the better the fuel the better the result -

REMEMBER: Octane does not equate to power - only to compressability prior to detonation - 100 octane being EQUIVALENT to only (100%) octane molecules (ie 8 carbons) compressability (relatively stable - but expensive) and 0 octane being equivalent to only (100%) heptane (ie 7 carbon molecules) molecues (pretty cheap but relatively unstable). So 95 is equivalent to 95% octane and 5% heptane molecules in regards to compressability prior to combustion - it is actually a lot of differnt length chains). Lower octanes are less compressable (ie can be used in lower compression engines) HENCE the 80Hp Rotax can take a lower octane fuel without detonation or pinking and the subsequent engine damage - or even destruction!

In days gone by TEL was added to improve compressability - ie Leaded fuel (or sometimes called Ethyl fuel). It was a low cost fix for the oil companies. Then the rules changed and they had tyo make a better TRUE quality fuel - and the motor industry had to change the designs - since they used the lead in the fuel as part of the engine design as asort of lubricant on the valve seats.

WATCH the ethanol content. O360 engines HATE ethanol - watch for seals and the like - and as Seb says the fuel lines and reservoirs (fiberglass tanks start to defibre with ethanol if the wrong resin is used). ROTAX are certain amounts of ethanol 'compliant' - see the Rotax site for the latest permissible E-blends (E10). Ethanol increases the risk of vapour lock and water being 'hidden' in the fuel and the seperation occuring at some time in flight!!!

My preferred 80/100HP engines are ROTAX running on unleaded MOGAS - and these engines are sweet! When you fly mission critical I promise that ROTAX is a saint! (we fly over rain forest for hours on end - if you go down you are for a few weeks to get out!). NOnetheless we source the best fuel we can from reputable dealers (we have the direct line to the head office of a major oil company that directs to good supplies when 'up country') and avoid fuel stations which have low turnover.

Octane decreases with storage - I have seen 100LL causing detonation due to extended poor storage in drums in the sun!

Rain has stopped so I can back out to play now (although the runway is underwater for the next 24 hours I am sure!!!
Comment by Stephen R. Smith on April 6, 2009 at 11:45am
Hi Donnie,

I have not tried Mogas with ethanol yet. That is my next experiment. I will report my findings. I expect lower temperatures and lower performance because ethanol has less energy in it. Your point about water in the gas is a good one. I will be checking the gascolator for water for sure.

Steve
Comment by Donnie Moore on April 6, 2009 at 1:53am
Did you happen to figure burn rate?
I would be interested to see the difference between pure mogas and the 10 Ethanol blend.
On my motorcycle I consistently get 10% lower mileage on 10% ethanol blended gas.
The one other thing to remember about ethanol is it's hygroscopicity. On the coast where you are that would be a concern to me. I would definitely put a gascolator inline and drain it often.
Comment by Stephen R. Smith on April 5, 2009 at 11:27pm
Thanks Sebastien and Bil for your comments.

I just completed my first experiment with Mogas in my Jabiru 3300. I filled one tank with 100LL and the other with Mogas without ethanol. I was able to get the Mogas at Lebanon (S30) in Oregon. Each time I switched tanks I observed RPM and EGTs. The Mogas seems to run just a teeny bit hotter then then 100LL. I saw no RPM change. Next I will try Mogas with ethanol which is all I can get here in California.
Comment by Bil Gillam on April 4, 2009 at 5:31pm
Hi, I have had no ill effects using auto gas with either the jabiru or 912 rotax. I had a titan tornado with close to 400 hrs and I have a jabiru 3300 today with 150 hrs I only use 100 low lead on trips. I don't have to use fuel with alcohol in Wy.
Comment by Sebastien Heintz on April 3, 2009 at 4:59pm
We get asked this question a lot, and we refer this question to the engine manufacturer. Of course, every engine type is different, so (obviously) what applies to a Rotax 912 ULS will not necessarily apply to a Jabiru 3300 (or a Continental O-200 and so on). Read the owner's / operator's manuals.

Regarding the Rotax: Rotax will be releasing the "liquids bulletin" in a revision on April 8th. It will again restate their position on fuels, with the exception that they now will allow E10 (10% ethanol) if the airframe builder (or whoever supplied and installed the fuel lines and filters) can confirm that those parts are compatible with such fuels. The ethanol (E10) issue is not about the Rotax engine itself, but the lines and filters.

As to using 100LL, their position has not changed and has been published by Rotax many times: They recommend that the oil be changed every 25 hours and not to use any pure synthetic oils with 100LL. Lead deposits may require cleaning of lead from the rings, valves and valve seats prior to TBO with frequent use (more than 30% running time) of lead.

Rotax owners and operator should subscribe to the Rotax Owners Assistance Network (ROAN) for email news and alerts regarding the use and operation of their Rotax aircraft engine: www.Rotax-Owner.com
Comment by Stephen R. Smith on April 2, 2009 at 6:15pm
Hello Bob,

I looked up your airport in airnav and also took a look with Google Earch. That is a nice setup you have and your tanker is a good idea.

I believe I am not allowed to store fuel at the airport in my hanger - not sure about that.

I see the L95 airport picture was taken by Paul Reinders. Paul gave me my checkride about two years ago. Its a small world.

Thanks for your comments.

Steve
Comment by Bob Jones on April 2, 2009 at 4:05pm
Stephen,first off I have a fairly unique situation , since my home is on a lake , and I declared it an airport , it is L95in the alaska fAA log, I fly only on floats and ski's, I have a trailer mounted fuel tank that holds 250 gallons , which I fill twice a year, the climate conditions are such that I have no fuel degradation, which form in hot climes.IE. algae etc.and Alaska does not have alcohol added fuel. ...BOB
Comment by Stephen R. Smith on April 2, 2009 at 3:44pm
I am hoping my Jabiru powered 601XL will tolerate the always-present ethanol we have here in California.
Comment by Thomas Richardson on April 2, 2009 at 3:41pm
I would add that at Zenith, it is the 701 that runs on the 100LL and still does to my knowledge.

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