M20J circa 79. left tank 93octane no ethanol

[Shadrach]

The IO 470J in my debonair has a compression ratio of 7-7.5, not sure the exact number.  It was designed to use the old 80 octain aviation fuel.  I can burn 87 ethanol free gas, but 90-91 is generally all that is available.  I burn around 11.5 to 12 gph to get 150 knots.  160 knots is all I can get around 4500' and ROP.  When I was looking at planes to buy the F & J money's were defiantly on my list.  I just found a nice Debonair first, and being able to burn mogas helped get the fuel cost down some.  

And as I said, I can tell no difference in what fuel I'm using.  I have been told that mogas is not good to let sit in the tank for long periods of time.  But I try to fly regularly.  And there is always some 100LL in there due to availability.

 

Do you segregate fuels or just mix in whatever is available?

[dmc]

Do you segregate fuels or just mix in whatever is available?

I mix, according to the STC this is not a problem.   The Debonair has three tank settings, left , right, and aux.  when I'm on the aux tanks unused fuel is pumped to the left tank.  So there is always going to be some mixing there.  I could keep one fuel in the right tank, and have thought about keeping 100LL in that side.  But since I have never had a problem, and have talked with others who primarily run mogas with no problems.  I just fill up with what's available.

[carusoam]

Mogas has gone below $2/gallon this week in NJ.  Credit card, regular grade....

An STC sure would be nice....

best regards,

-a-

[I have this friend..]

All, great discussion btw! 

Pun intended here is more fuel...

My friend would love to get an STC.

Under the impression it is not possible with a 79 M20J.

Does anyone know if this is true? (Lycoming 200hp IO-360 A36BD I believe.

Question: regarding boiling fuel (I find it hard to believe fuel at 4500 ft would boil with slight suction head (mechanical pump is aprox 1 foot above mean fuel level?) But in the event it did, Isnt boost pump even lower? Need to look at a parts manual.

12000 ft might be more of a concern. Although by the time u got to 12k on 100LL u probably would not have hot fuel or at least in the lines from fuel level to pump inlet assuming you are not taking off from colorado).

Someone mentioned different blends based on season.  Question: if it is advertised as ethanol free and you test it for ethanol free, and MTBE is no longer allowed. What else are they adding that is a concern? I was under the impression that gasoline with no MTBE or ethanol was not going to hurt tank sealant or internal seals hoses etc..

Regarding longevity of fuel, any thoughts on using "stable" its amazing how well it works with boat fuel storage. Not that I would imagine leaving in tank for long time.

Regarding cost savings. A round trip flight from say Georgia or Carolinas to NY or Vermont the savings is easily enough to make it cheaper than a commercial flight. Its can easily be $3.00 cheaper per gallon.

Agreed none of this is worth it if an accident is caused. On the other hand if 100LL becomes scarce this is what will happen. I imagine if user fees for FAA services occur things are not going to get safer either.

I agree it would be safer to use 100 LL.

But..

It seems it is possible to use auto fuel if you are extremely careful and only use it in certain circumstances..

And..

It would be safer to fly an aircraft with fixed gear. Yet people fly all the time with retractable gear. Anyone else ever have a failed gear motor?

It would be safer to fly only in the day time. Why would anyone fly at night?

It would be safer to not fly IFR

It would be safer to fly with two engines. Who would risk flying with only one engine?

Any twin owner would first ask you where your second engine is before asking what is in your tank.

It would be safer to not fly at all.

It might be safer if all general aviation went away

Its all calculated risk. Is flying 93 octane ethanol free the most dangerous irresponsible thing you can do with your aircraft? Does anyone know if this is a statistically significant cause of crashes?

Probably not a valid question because no idea how many people are actually doing it.

[kortopates]

I am no expert on this. But it does take approval of both the engine and the airframe separately. My understanding is that the Mooney airframe testing failed to meet the requirements (but I don't recall the specific airframe but supposedly it included a Lyc engine approved for mogas). In other words the effort was made to get approval and it flunked. I recall Aaronk25 went into it in more detail in an earlier post. Isn't that enough reason not too?

Incidentally, I've only gotten vapor lock once in my Mooney in over my dozen years of flying it and it wasn't on take-off or on climb to altitude which are the much more common ways. My one event was from flying over the hot Arizona desert mid summer at probably about 10-12k'. Electric boost cleared it right up for me.

BTW Your electric boost is at the same level as the fuel selector valve almost adjacent to the gascolator and just immediately downstream of it.

Edited September 24, 2015 by kortopates

[carusoam]

IHTF,

I think you may be missing something important.  

Search for it.

Find it.

Then overcome it.

Document how you overcame the challenge.

Work from facts that exist.

Your line of questions is coming across more like somebody has done you wrong...big oil or big government...

Keep focussed on the challenge...

Define what the challenge really is.

Determine solutions for each challenge or determine that the challenges no longer exist.

Asside from that, try to understand what makes different fuels evaporate, differently.  Temperature and pressure are key to the evaporation rates. Try to understand how different fuels destroy the various seals and sealants.

The danger comes with doing something we don't fully understand.  Training allows us to take steps without knowing everything. In this case we rely on an expert to show us the way and point out the areas we want to avoid.

[carusoam]

A small amount of research on various STCs could go a long way.

One poster has given you insight how a particular automotive fuel is good in his STC.

Another one gave you limitations of CR and lower octanes.

Your reply comes across in a similar fashion of a person that is willing to try something because it sounds right.

That the odds seam to be favorable.

Before I put a different fuel in my plane, I would want to know that every seal, sealant and hose will not swell or degrade over time.  That the compression ratio is acceptable to automotive fuels in my engine with my Pistons...

Every now and then our community loses a fuel injector with something stuck in it.  That something gets past screens and filters. It is a crummy expensive experience.

Of course every now and then our community loses a plane due to things getting in the fuel like water, or not enough things in the fuel tank like gallons of gas.

It is a real challenge to follow all the rules all of the time.  But there is a well defined method to go around them.  That is the STC process.

What if all it takes is to use the right sealant in the fuel tanks.  Or swap out a few O-rings in the fuel injectors.  Or run 200°F ROP or 100°LOP...

There are at least two STCs being generated by people at MS.  It would be great to have a third.

Edited September 24, 2015 by carusoam

[carusoam]

I think what would work better is asking the question slightly differently...

"What would it take to get an STC for a Mooney to use automotive fuels like DMC quoted above?"

Follow up with the STC work that Paul has pointed out.  What if the challenges back then have been overcome.  We have a whole bunch of new materials from gas cap O-rings to fuel tank sealants.

There is a huge amount of potential savings. Not chasing any of the loose ends comes across as being disingenuous.

Try to not appear as being disingenuous, you may get a larger response.

Best regards,

-a-

Edited September 24, 2015 by carusoam

[jetdriven]

You still have to run ethanol-free gasoline. My understanding is with the EPA mandate, that's nearly impossible to find.  None in Texas, for example. 

[dmc]

You still have to run ethanol-free gasoline. My understanding is with the EPA mandate, that's nearly impossible to find.  None in Texas, for example. 

I use Air Nav when planning a trip.  It's true that it's not everywhere, and many times it makes no sense to go very far out of the way.  But it is out there.  Thankfully here in Florida many don't like to use fuel with ethanol in their boats so it's not hard to find.  The airport I'm based at does not have it, but the Sunoco station that is on the way does.  I just fill up a few 5 gal cans and fuel the plane myself.  This also saves me from having to taxi down to the self service pumps.  The pure gas website list 99 stations in Texas.  Not sure how many airports have it.

i still use quite a bit of 100LL, most airports don't carry both.  But when it's available it usually around a dollar a gallon cheaper.  It works for me because it is available here, and at several airports in the mid- west where I frequent.  

 

[aaronk25]

A small amount of research on various STCs could go a long way.

One poster has given you insight how a particular automotive fuel is good in his STC.

Another one gave you limitations of CR and lower octanes.

Your reply comes across in a similar fashion of a person that is willing to try something because it sounds right.

That the odds seam to be favorable.

Before I put a different fuel in my plane, I would want to know that every seal, sealant and hose will not swell or degrade over time.  That the compression ratio is acceptable to automotive fuels in my engine with my Pistons...

Every now and then our community loses a fuel injector with something stuck in it.  That something gets past screens and filters. It is a crummy expensive experience.

Of course every now and then our community loses a plane due to things getting in the fuel like water, or not enough things in the fuel tank like gallons of gas.

It is a real challenge to follow all the rules all of the time.  But there is a well defined method to go around them.  That is the STC process.

What if all it takes is to use the right sealant in the fuel tanks.  Or swap out a few O-rings in the fuel injectors.  Or run 200°F ROP or 100°LOP...

There are at least two STCs being generated by people at MS.  It would be great to have a third.

At 200rop, even 100rop or 50lop auto fuel will run great even at higher chts. The only issue I've seen is around 20rop the mixture is almost vulnerable to staring to burn before the spark. All other mixtures make it more stable and allow for higher cht operation. I've seen 400cht mixture where the only change implemented was going to full rich immediately dropped the chts.

The critical part of the STC would be putting fuel pumps I the tanks, like autos. I'm not sure if vapor lock on summer blend fuel is even a issue any more. The gas today resembles more of the quality a of aviation fuel than the car gas of 20 years ago when vapor pressures were high. I only meant to sound a bit cautious or warning as I'd hate to say somthing then someone takes the liberal view of the intent and gets hurt.

Auto fuel would also let us run full synthetic oils and most likely extend our oil change intervals!

Wish it could happen!

[N201MKTurbo]

I would think you could get alcohol free fuel if you ordered it that way. The alcohol is mixed at the terminal. As long as they knew it was going to non-road use. You would have to work it out with the supplier. Thinking of my jet war bird friends, you would be amazed at what they will sell you if you show up with a tank truck! Experimental fuel for an experimental jet! Taxes? what taxes? We don't need no stinkingTaxes!

Edited September 25, 2015 by N201MKTurbo

[Shadrach]

I bet farm diesel would run great in a lot of the Cold War era jets. Especially the old Migs.

[WardHolbrook]

The length of time, effort, and FAA risk your friend went to save about $0.30/gallon.

(These numbers assuming 20% mogas / 80% 100LL.  $2.50/gallon 93 octane with no ethanol and $4.00 avgas.)

*Totally not worth $15 saved on a 50 gallon, 800nm trip*.

EDIT: oh wait, there's only 32 gallons in the one tank.  So he's saving all of $9.60 on the 500nm he will be able to travel if he were LOP on that left tank.

The phrase "Penny wise and pound foolish." comes to mind here. 

[N201MKTurbo]

I bet farm diesel would run great in a lot of the Cold War era jets. Especially the old Migs.

60 % industrial kerosene 40% farm diesel. Works great.

[carusoam]

Summarizing...

1) I have 100 gallons of capacity

2) current price in NJ is about $4 per gallon for avgas.

3) $2 per gallon for Mogas.  Fall is crushing the price of fuels...

4) without an STC, the economic risk of damaging the plane is worse than the $200 in saving.

5) having a proper STC is worth an AMU to get the $200 each time I were to fill up.

6) some specialty fuel suppliers may not appreciate the renewed competition of Mogas...

7) insurance company and FAA will want to see the STC, in the event of a serious accident related to the fuel choice.

Many Pros and Cons,

-a-

[dmc]

The phrase "Penny wise and pound foolish." comes to mind here. 

I bought the STC even though it only amounted to putting some stickers next to my fuel tank saying that I was allowed.  I comply with everything else to stay legal even though I may not agree on some items.  Like not being able to use the same avionics as the experimentals.  

[garytex]

 One of the very last DC3 freight guys I knew ran hundred low lead in one tank  for takeoff and climb, car gas in the other tank for cruise.  And I put about 700 hours on a Cessna 170,  C-145 engine which has 7.5 to 1 compression ratio on car gas in the days before it was ruined with alcohol.  It ran fine, and only had gravity flow head pressure.   I watched it close for vapor lock but never experienced it. Occasionally I would also get a tank of hundred low lead and look  pretty hard at the EGT's to see if I could determine if there were any volatility differences.  Found none. 

 In the future, if alcohol free gas became available in Texas, and there was an STC, cargas might be the answer to some future kind of hundred low lead loss for us.

[Shadrach]

 

 One of the very last DC3 freight guys I knew ran hundred low lead in one tank  for takeoff and climb, car gas in the other tank for cruise.  And I put about 700 hours on a Cessna 170,  C-145 engine which has 7.5 to 1 compression ratio on car gas in the days before it was ruined with alcohol.  It ran fine, and only had gravity flow head pressure.   I watched it close for vapor lock but never experienced it. Occasionally I would also get a tank of hundred low lead and look  pretty hard at the EGT's to see if I could determine if there were any volatility differences.  Found none. 

 In the future, if alcohol free gas became available in Texas, and there was an STC, cargas might be the answer to some future kind of hundred low lead loss for us.

Gravity flow head pressure is ideal for car gas. It's the self priming systems that pull fuel up hill that have problems meeting FAA requirements.

Edited September 28, 2015 by Shadrach