Aviation Fuel Use

Towmanjim said:

Loved all the inuiput, thanks to all. Probably will not run any avgas, but I am convinced that non-ethanol gas is much better. When I am forced to run the ethanol it pings under acceleration. Pretty sure that is poor gas. Guess I have to try to rely on PureGas to get me to stations that have non-ethanol. Always fuel up before I get back to the PHX area.

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Well of course non-ethanol fuel is better. Gasahol is a burearucratic concoction, not a chemical one. I continue to believe the advice printed in my 1985 Haynes Manual which advised, "Avoid the use of motor fuel adulterated with alcohol."

The only informed people who support ethanol fuels are corn farmers or work for Cargill or ADM.

Was noted above that the engine will electronically prevent pinging.

Your gas may be "bad" because it's regular instead of premium. Or your "acceleration" is attempted in a too-high gear, i.e. you're lugging it. With these engines it's my procedure to never attempt (or expect) acceleration in gears above 2nd from anything lower than 4K rpms.

Either that or you have a tuning or component problem that needs to be corrected outside of fuel choice.

As others have pointed out, running leaded avgas or leaded racing fuel in an engine designed for unleaded fuel is a big no-no. On the other hand if you can find non ethanol fuel of suitable octane, go for it. Check out www.pure-gas.org for suppliers in your area. I bought some 91 octane non alcohol fuel at a Country Mark station in Tipton, Indiana yesterday for $3.50/ gal. Unfortunately, the octane pool has been lowered in recent years due to the near universal adaptation of motor fuels with 10% and higher ethanol. Many refiners now produce two grades of non ethanol fuel--85 octane and 91 octane, knowing that the 10% ethanol addition (done at the terminal) will bump the final octane to 87 and 93.

I did run avgas in my bike (not my BMW) for years. My Turbo runs with an 810 kit, 25 lbs. of boost and 10:1 compression. I did just recently switch to VP Racing Fuel (114 octane). BTW, I stopped at a Chevron gas station in Needles, CA. on my way home from California last week that sold Avgas at the pump. Never saw that before as I always bought my gas at the airport.

Towmanjim said:

Loved all the inuiput, thanks to all. Probably will not run any avgas, but I am convinced that non-ethanol gas is much better. When I am forced to run the ethanol it pings under acceleration. Pretty sure that is poor gas. Guess I have to try to rely on PureGas to get me to stations that have non-ethanol. Always fuel up before I get back to the PHX area.

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I'm going to be the contrarian. There's nothing wrong with E10 Gasohol. After running it for a few tanks your BMSK adapts to it and you can't tell the difference.

The energy content of pure gas is 150K BTUs per gallon, gasohol is about 145K or 4% less so your BMSK pumps 4% more fuel into the combustion chamber.

The better news is that where the Octane rating of gas is 91/92, the Octane rating of Ethanol is 108, which is one of the reasons it makes a good addition to fuel. http://en.m.wikipedia.org/wiki/Gasoline.

I'm not a fan of growing corn and turning it into fuel ... just adding a counterpoint.

My experience with ethanol blends is that it runs fine as long as it's
not stale. After 30 days without stabilizers I can sure feel the difference
with small engines. Never have knowingly put stale ethanol blends in my RT
I cannot say how an RT would react.
That said I'm not the only one who would say there is a very noticeable
increase in fuel economy when I use pure gas in my RT. I'm not good enough to
detect any power difference though. A reason (besides safety) I gave up
on my airhead was that modern fuels require modern control systems
to work properly. One can complain all you want but ethanol fuel is here to
stay. If you need more power from your bike work with the system and fuel
available, or better yet, get a more powerful bike. Don't foul your bike
with lead.

roger 04 rt said:

I'm going to be the contrarian. There's nothing wrong with E10 Gasohol. After running it for a few tanks your BMSK adapts to it and you can't tell the difference.

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I won't dispute this specific statement as it relates to fuel economy on late model oilhead/hexhead/camhead bikes. But would vehemently disagree as it regards to the dissolving of the rubber fuel pump mounts in classik K bikes and the disintegration of fuel lines and carb floats on Airheads. It is also probable that other brass components, and fuel pumps suffer shortened life.

So, not to belabor the point but I do think there are things wrong with E-10 Gasahol.

lkchris said:

Was noted above that the engine will electronically prevent pinging.

Your gas may be "bad" because it's regular instead of premium. Or your "acceleration" is attempted in a too-high gear, i.e. you're lugging it. With these engines it's my procedure to never attempt (or expect) acceleration in gears above 2nd from anything lower than 4K rpms.

Either that or you have a tuning or component problem that needs to be corrected outside of fuel choice.

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It's a matter of trust insofar as octane at the pump. Could be that 91 sits longer at certain stations. Most of the time it's in lower gears under hard acceleration at or above 4K RPM. The only difference from Iowa is that I have put in iridium plugs. I am going to change the plugs soon and try the OEM.

PGlaves said:

I won't dispute this specific statement as it relates to fuel economy on late model oilhead/hexhead/camhead bikes. But would vehemently disagree as it regards to the dissolving of the rubber fuel pump mounts in classik K bikes and the disintegration of fuel lines and carb floats on Airheads. It is also probable that other brass components, and fuel pumps suffer shortened life.

So, not to belabor the point but I do think there are things wrong with E-10 Gasahol.

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To your points, we have no disagreement. I would add that phase separation is also a risk, too much water and the ethanol and it combine and it sinks to the bottom of the tank. The result being that your Octane is now several points lower due to the ethanol dropping out.

Towmanjim said:

Just curious if anyone has had any experience using 100 Low Lead aviation fuel in their bike. Mine, 05 1200GS seems to run better with octanes above 90. It is also nearly impossible to get 100% gasoline in the Phoenix area.

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I've run 100LL in my old bikes for years, it works well. Alittle lead for the old valve seats. And it doesn't leave the crud behind when it evaporates. It will keep for some time in a sealed can.

New bikes don't need the high octane and the lead content will wreck the catalytic converters.

Ave gas is alittle cheaper than race gas. Unleaded race gas is available at $9/$10 a gallon.

Eclipse Gas

Thanks for this thread. I'm going to a remote area (Stanley, Idaho) to view the August 21, 2017 eclipse and was thinking of potentially using 100LL Avgas in my 2017 R1200GS (but only if needed, and car gas were to be unavailable) because there will be plenty of planes of friends where I am going but changed my mind after reading this thread. I had forgotten about the catalytic converter and oxy sensor issues. My 2017 moto is too "modern" for me to chance screwing things up. If I started getting a bunch of (expensive) codes I would be very unhappy.

I have an airplane that requires Avgas (100LL) so have experience with that. My understanding is that, besides the octane boost, the lead content serves to lubricate the valves, e.g., stems and seats. The plugs end up being a little more dirty than on cars and motos, I think, but is quite manageable. Developing a no-lead high-octane alternative for these old engines designed originally for 100 octane fuel has been not-easy-to-fix problem. See <https://en.wikipedia.org/wiki/Avgas> And these engines by today's standards have surprisingly low power for their displacements and very low compression ratios.

As an anecdote, as a kid I raced Go-Karts where we typically ran 100% methanol. Methanol was preferred over gasoline of any grade, since it didn't carbon up the cylinders, rings, etc. The cylinders and pistons were spotless after using it. I don't know if my methanol experience translates to ethanol, or not, but I suspect many alcohols are similar. We had to re-jet to push a relatively larger amount of methanol through for the same power (e.g., methanol got less "mileage.")

My understanding is that octane rating itself doesn't do anything for power, but does allow for higher compressions and more aggressive ignition advance, both of which can increase power in engines designed for these things.

Notwithstanding, I do use non-ethanol gas where conveniently available, but it is often not convenient, even with the PureGas app, so I mostly use ordinary pump gas. But, I speculate that non-ethanol gas might tolerate storage better than the gasolines with ethanol added so use it where I can, particularly in the off-season, where the bike might not be used for a while. But mostly I just figure my modern 2017 bike is designed to do just fine with up to 10% ethanol in the fuel and don't worry about it.

My '05 RT owners manual reads "use 97 ROZ grade premium fuel" and I have been getting Shell premium gas with a 93 octane level for about $2.55/gal. and getting an average mpg of 51.1 and the bike runs great. I have not been able to find any higher grade gas in LA.
I have been thinking about going to the 87 octane to see what happens and maybe save a few bucks. Any potential risks about trying this?

baronk said:

My '05 RT owners manual reads "use 97 ROZ grade premium fuel" and I have been getting Shell premium gas with a 93 octane level for about $2.55/gal. and getting an average mpg of 51.1 and the bike runs great. I have not been able to find any higher grade gas in LA.
I have been thinking about going to the 87 octane to see what happens and maybe save a few bucks. Any potential risks about trying this?

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We use AKI in the US.
98 ROZ is 91 AKI
95 ROZ is 89 AKI
91 ROZ is 87 AKI

You may be ok with 89 AKI but 87 AKI is probably too low to use on a regular basis.

Thanks for the conversion data; I think I will drop down one grade and see what happens.

jkjohnson said:

Thanks for this thread. I'm going to a remote area (Stanley, Idaho) to view the August 21, 2017 eclipse and was thinking of potentially using 100LL Avgas in my 2017 R1200GS (but only if needed, and car gas were to be unavailable)...

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You won't have any problem finding good gasoline in that area of Idaho.