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Mogas


Flymu2

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Random thoughts on auto gas in airplanes:

1) Not designed for it

2) Vapor pressure much higher and inconsistent due to seasonal blend variations

3) Chemistry that can attack parts of airplane fuel systems

4) Forms gum and varnish more easily

5) Hassle factor getting it to your airplane.

6) The premium auto gas may be  $1 to $1.50 cheaper than avgas. Say, $10/hour savings. Private airplane use probably runs 50 to 100 hours per year. Annually saving you $500 to $1000

7) If you are worried about 0.5 to 1 AMU in cost savings.....IMHO if that's a big deal, then airplane ownership may not be for you.

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2 hours ago, MikeOH said:

Random thoughts on auto gas in airplanes:

1) Not designed for it

2) Vapor pressure much higher and inconsistent due to seasonal blend variations

3) Chemistry that can attack parts of airplane fuel systems

4) Forms gum and varnish more easily

5) Hassle factor getting it to your airplane.

6) The premium auto gas may be  $1 to $1.50 cheaper than avgas. Say, $10/hour savings. Private airplane use probably runs 50 to 100 hours per year. Annually saving you $500 to $1000

7) If you are worried about 0.5 to 1 AMU in cost savings.....IMHO if that's a big deal, then airplane ownership may not be for you.

Saving an AMU or two everywhere is what allows me to own an airplane...   :)

Unfortunately, all the other details Mike covered are pretty much the reason other fuels never get very far...
 

If they could perform today... the specs would change tomorrow... with or without you knowing it...

Rubber seals and sealants are sensitive to fuels...

All the way up to diaphragms and seals inside the engine...

 

The IO550 doesn’t need 100LL... but it still requires 100 octane...

Getting the octane without the lead would be great...

Without raising the price... (I’m a CB at heart)
 

So... MoGas had a spec at one time... and some airports had both...

But... going to the gas pump downtown... may get alcohol included in it depending on the weather...

It would help to be a chemical engineer to know what’s going on with fuels all the time... but even then ChEs don’t want to put up with all the weirdness that can be involved on a daily basis... when it comes to fueling their plane.

Best regards,

-a-

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Also today auto gas has so many additives the existing stc’s are mostly dead. Used to be able to run mogas in the Aeronca and cub but the faa disallows all mogas with ethanol. So you’d have to go to the boat dock and pay $6/gal for ethanol free mogas. 
 

-Robert 

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Forgot about the ethanol problem. It’s hard to find ethanol free mogas.

What spurred my question was Mike Busch’s recent EAA video about sticking exhaust valves. It would be really nice not to have lead in our fuel, but it hasn’t been easy to work that out.

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Also today auto gas has so many additives the existing stc’s are mostly dead. Used to be able to run mogas in the Aeronca and cub but the faa disallows all mogas with ethanol. So you’d have to go to the boat dock and pay $6/gal for ethanol free mogas. 
 
-Robert 

$6/gal? Where, California? Here in Florida it’s more like $3.50.

Octane is so low, I think 93-94 would be doable in our engines, with different timing.
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Mooneys were never STC'd for the stuff.  Don't know why, probably BS.  Not reason the O360 in mine can't burn mogas.  No vintage aircraft can burn mogas with booze, though.  Some of the new Rotax airplanes can.  Heck, why not?  The engine started out as a car engine. Even if mine were STC'd it woudn't be worth it.  The only places I can get booze-free mogas are marinas, and they're pricey as well.  Gotta bend over and take it like a man.  

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11 minutes ago, carusoam said:

The nice thing about two tanks... T/O and climb on one tank... cruise on the lesser quality fuel in the other...

If that ever become a possibility...

Best regards,

-a-

And, like no one would ever screw that up and toast their engine running on the wrong tank.  Yeah, a few thousand $ here and there do add up.  But, there are limits to how much of a CB I am.  Running mogas is well past that limit.  Much easier and less risky ways to save money.

Edited by MikeOH
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It’s not about money for me. It’s about reliability and maintainability. Also, sooner or later unleaded fuel will be required. Hopefully there will be a fuel available to meet that requirement.

It's crazy we're still waiting on it. It seemed like we were getting pretty close till the Feds dropped it as a priority. ;(


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As Mike pointed out...

Simply getting the wrong fuel, or selecting the wrong tank for T/O and climb can make the lesser fuels dangerous within a few minutes...

Detonation eliminates the boundary layer at the surface of the piston... once removed the piston top sees the full temperature of the flame temp of gasoline and oxygen...

Piston crowns melt in minutes...

PP thoughts only, not a mechanic...

Best regards,

-a-

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25 minutes ago, kortopates said:


It's crazy we're still waiting on it. It seemed like we were getting pretty close till the Feds dropped it as a priority. ;(


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It tells me that the market is sooo small that without government subsidies or forced regulation there is zero reason for industry to invest in a solution.  Frankly, the fact that it is such a small market tells me it's a REALLY REALLY insignificant environmental problem, too.  This is a political issue.  I'm hoping someone in the government figured this out and decided the status quo is just fine.

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13 minutes ago, MikeOH said:

It tells me that the market is sooo small that without government subsidies or forced regulation there is zero reason for industry to invest in a solution.  Frankly, the fact that it is such a small market tells me it's a REALLY REALLY insignificant environmental problem, too.  This is a political issue.  I'm hoping someone in the government figured this out and decided the status quo is just fine.

That may well all be true, after all it was an EPA suit that seemed to get things going too. I never put that much stock in the pollution we were doing with our low lead, but  I am very convinced our engines would run a lot cleaner, which in turn would reduce maintenance, allow better lubricants and increase  engine longevity, if we could just run without leaded gas! Those are benefits I am eager to see. Although  whatever octane booster they come up for unleaded 100 avgas could turn out be worse in some unforeseen way, I optimistic we'll see benefits.

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31 minutes ago, MikeOH said:

This is a political issue.

I agree. We are, however, at the mercy of the one company that makes TEL. If something happens to it we're SOL. I think also that we're not entirely politically impotent. Most of the training fleet uses 100LL. Absent COVID there will be strong demand for trainers. Are they all going to change suddenly to diesel or Rotax? Also, all those engines are manufactured outside the US. Consider Cape Air and some of the small cargo feeders. We may be small, but can still be significant.

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1 hour ago, Flymu2 said:

I agree. We are, however, at the mercy of the one company that makes TEL. If something happens to it we're SOL. I think also that we're not entirely politically impotent. Most of the training fleet uses 100LL. Absent COVID there will be strong demand for trainers. Are they all going to change suddenly to diesel or Rotax? Also, all those engines are manufactured outside the US. Consider Cape Air and some of the small cargo feeders. We may be small, but can still be significant.

Most of the avgas burnt however is burnt in a small fraction of work horse airplanes that largely are running large bore engines that must have the high octane.  I forgot the actual numbers but I want to say by poor memory it is something like 80% of fuel is burnt in must have high octane engines.  Mail, freight, some scheduled carriers, and us few odd ball real GA folk.

I strongly doubt that they will end access to 100LL without  a suitable replacement, otherwise stranding a large fraction of the us are infrastructure.

I wonder if it would be cheaper to just buy everyone who has a high octane must engined airplane a new airplane that burns with a modern fadac engine than retool a massive fuel industry even if it is a boutique corner.

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1 hour ago, aviatoreb said:

I wonder if it would be cheaper to just buy everyone who has a high octane must engined airplane a new airplane that burns with a modern fadac engine than retool a massive fuel industry even if it is a boutique corner.

If only

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2 hours ago, kortopates said:

That may well all be true, after all it was an EPA suit that seemed to get things going too. I never put that much stock in the pollution we were doing with our low lead, but  I am very convinced our engines would run a lot cleaner, which in turn would reduce maintenance, allow better lubricants and increase  engine longevity, if we could just run without leaded gas! Those are benefits I am eager to see. Although  whatever octane booster they come up for unleaded 100 avgas could turn out be worse in some unforeseen way, I optimistic we'll see benefits.

Good points, Paul.  Auto engines were driven to eliminate lead in fuel as it destroys catalytic converters.  Somehow, engines/valves were designed to NOT require lead.  Not sure why aircraft engines can't take advantage of that technology.  Only thing that comes immediately to mind is that the technology doesn't work at the high continuous power outputs required of aircraft piston engines.

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What interesting is on the M20C, the TCDS states 100LL minimum, but on an M20D, same airframe and engine, states 91/96 octane minimum.

M20C: Lycoming O-360-A1D or O-360-A1A (Carburetor MA4-5, Flow Setting P/N 10-3878, 10-3878-M, or 10-4164-1). Fuel 100LL or 100/130 min. grade aviation gasoline
M20D: Lycoming O-360-A1D or O-360-A2D (Carburetor MA4-5, Flow Setting P/N 10-3878, 10-3878-M, or 10-4164). Fuel 100LL or 91/96 octane min. grade aviation gasoline

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1 hour ago, Raptor05121 said:

What interesting is on the M20C, the TCDS states 100LL minimum, but on an M20D, same airframe and engine, states 91/96 octane minimum.

M20C: Lycoming O-360-A1D or O-360-A1A (Carburetor MA4-5, Flow Setting P/N 10-3878, 10-3878-M, or 10-4164-1). Fuel 100LL or 100/130 min. grade aviation gasoline
M20D: Lycoming O-360-A1D or O-360-A2D (Carburetor MA4-5, Flow Setting P/N 10-3878, 10-3878-M, or 10-4164). Fuel 100LL or 91/96 octane min. grade aviation gasoline

And, luckily for all of us with carbureted engines, they've all been approved by Lycoming to run on 94UL.  So when/if 100LL goes away, hopefully it'll be a fairly simple airframe approval for us.

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