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Documentation for testing with unleaded/mogas?

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skirting_virga

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My 8A specifies 100LL in the POH and on the tank fillers, but I would like to start experimenting with a mogas mix (initially 25%, then 50% and possibly up to 75% eventually) for cruise. Cost is a secondary consideration - my goal is to reduce the potential lead deposits in the cylinders, plugs, and oil. UL94 is not readily available locally, but non-ethanol gasoline is. I operate at high density altitude and don't anticipate any trouble with knock, although it is comforting to think that even a small proportion of 100LL confers a significant vapor pressure and antiknock benefit.


What do I have to do to "legally" change the plane to allow the use of other fuels? Does this require an engine logbook entry?
 
skirting_virga said:
My 8A specifies 100LL in the POH and on the tank fillers, but I would like to start experimenting with a mogas mix (initially 25%, then 50% and possibly up to 75% eventually) for cruise. Cost is a secondary consideration - my goal is to reduce the potential lead deposits in the cylinders, plugs, and oil. UL94 is not readily available locally, but non-ethanol gasoline is. I operate at high density altitude and don't anticipate any trouble with knock, although it is comforting to think that even a small proportion of 100LL confers a significant vapor pressure and antiknock benefit.


What do I have to do to "legally" change the plane to allow the use of other fuels? Does this require an engine logbook entry?
Click to expand...

You are not under any regulatory restrictions that prevent you from using any fuel you wish. Many RVs have been flown with auto fuel for the past few decades. There are operational considerations in regard to various seasonal blends of auto gas and specific engine configurations but these don't fall under any FARs.

Also, your POH does not carry any regulatory weight since a POH is not required for aircraft with an experimental airworthiness certificate and not part of the airworthiness process.
 
skirting_virga said:
What do I have to do to "legally" change the plane to allow the use of other fuels?
Click to expand...
Having 100LL labeled at tank filler location will be a problem if you intend to use full-service fueling. Most mogas/Swift94 are self-serve pumps but some locations, KJOT Joliet, IL for example, mogas is full-service only.
 
As a follow up to this topic. Perhaps there will be an ever increasing level of interest in using 91 octane unleaded auto fuel in our Lycoming engines going forward.

This increasing interest may be driven by a multitude of factors: 1) The political debate over 100LL (environmental, closing airports due to lead, etc). 2) A desire on the part of owners to gather the benefits to their engines by getting the lead out. 3) The potential of larger economic forces pushing the issue (cost of 100LL vs 91 unleaded). And other factors.

With these potential driving forces, and the prospect of many folks involved doing their own "testing" -- to understand more about the risks, benefits, best management procedures, of using 91 unleaded, would it make sense to start a new forum on 91 unleaded auto fuel?

Some of the questions and discussion might include: Implications of compression ratio on fuel decisions. How to manage fuel sources for different compression ratios. Different approaches to using 91 unleaded such as: dedicated fuel tanks vs blending. If different tanks are used, how to manage the source to avoid detonation or other adverse events.. If blending is used, what is the best ratio for different types of missions. If using dedicated tanks, when to switch from 100LL to 91, and back to 100LL (what altitude, what type of flight operations, are leaning procedures used with 91 unleaded, if leaning is used are there best management procedures, etc)? What are the different considerations for EFI vs Carb type fuel systems? Does the use of 91 unleaded result in any adverse effects on engine (valve guide wear, valve recession, etc)? How about vapor lock, and best practices to avoid this risk? What steps should be taken to document this testing, and decisions on how to manage the fuel system (modifications to the "POH" - at least the POH as referenced on VAF)? How about the use of advanced ignition systems that are mapped to MP? And many more questions and nuances.

Rather than each of those that are interested in this topic, pursuing their own "testing", and randomly sharing their efforts on various forums, perhaps a more strategic approach would be to have a focused forum (maybe something like "Using 91 unleaded auto fuel") under one of the main headings. Under this scenario, folks that have already made some headway on this topic could share their approaches and lessons learned, and those that are "testing" can benefit from their wisdom, as well as contribute to the cause. Maybe there is already a forum that could host this type of discussion, but in my review, in my humble opinion, I couldn't find any forum titles that would automatically draw my attention to this topic.

FWIW - I personally don't buy into the whole environmental/human health risk dialogue that is being used to shut down 100LL and close AIRPORTS. The risk assessment methodology used in the 100LL analysis is just too full of leap of faith assumptions and very casual cause and effect assumptions. But, once the narrative gets started, it's very difficult to bring common sense (and reasonable science) into the discussion. On the other hand, if a Lycoming will run cleaner, and longer (ie, more TBO), while at the same time costing less to run, then I'm on board that train.
 
If your plane has the Andair fuel selector, I think there is an SB against using autogas due to the incompatibility with the alcohol content in the fuel.
There was also a post I recall about Proseal reverting to goo from someone using autogas almost exclusively. I haven't heard of anything about the Lycoming engine having any issue with autogas on VAF.
 
PhatRV said:
If your plane has the Andair fuel selector, I think there is an SB against using autogas due to the incompatibility with the alcohol content in the fuel.
There was also a post I recall about Proseal reverting to goo from someone using autogas almost exclusively. I haven't heard of anything about the Lycoming engine having any issue with autogas on VAF.
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The RV-12 and -12iS can use ethanol-blended mogas exclusively (in fact, it is recommended by Rotax over 100LL). The fuel tank in the -12 uses the same sealant as other RVs, currently the ChemSeal Flamemaster that replaced Proseal. Don't know about the Andair valve.
 
jsalley said:
The RV-12 and -12iS can use ethanol-blended mogas exclusively (in fact, it is recommended by Rotax over 100LL). The fuel tank in the -12 use, currently the ChemSeal Flamemaster that replaced Proseal. Don't know about the Andair valve.
Click to expand...
When did this switch occur? I'm trying to figure out what year the tanks would have needed to be constructed to use the newer rather than the older sealant.

wsquare said:
With these potential driving forces, and the prospect of many folks involved doing their own "testing" -- to understand more about the risks, benefits, best management procedures, of using 91 unleaded, would it make sense to start a new forum on 91 unleaded auto fuel?
Click to expand...
I like this idea, but I would expand the scope to involve all auto gas - ethanol or non-ethanol, 85-93 octane, etc.
 
PhatRV said:
If your plane has the Andair fuel selector, I think there is an SB against using autogas due to the incompatibility with the alcohol content in the fuel.
There was also a post I recall about Proseal reverting to goo from someone using autogas almost exclusively. I haven't heard of anything about the Lycoming engine having any issue with autogas on VAF.
Click to expand...
I've been doing both of those things for 8 1/2 years and 1700 operational hours, no problems yet. When do they start?
 
@skirting_virga. "I like this idea, but I would expand the scope to involve all auto gas - ethanol or non-ethanol, 85-93 octane, etc."

Thanks for expressing support for a forum on the topic of auto fuel. The continued posting on this thread tends to emphasize the idea of a forum on the topic. Agree that the topic should include all auto gas. Good point. After all, the use of auto fuel may be in our collective future, eventually... Whether we like it or not...
 
airguy said:
I've been doing both of those things for 8 1/2 years and 1700 operational hours, no problems yet. When do they start?
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I just want to point out the things that were posted in VAF before. Not validating any fact because the experiences are anecdotal at best.
 
Every so often someone wants to reinvent the wheel or in this case the use of mogas in our Lycomings.
I have used Mogas E10 for the last 800 hours and 14 years of trouble free flying in my RV-10.
Many others on this forum have more than 1000 hours on mogas and one I can think of, over 2000 hours.
Much like the OP, saving money was not my prime motivation but rather, exercising the freedom to experiment and having an alternative fuel source
in case the loonies in CA decide to do away with 100LL.
My 8A specifies 100LL in the POH and on the tank fillers,
Click to expand...
Add a page and a sticker that says: may use 91 Octane E10

The old wife's tale about your tank sealant dissolving is, well, just that.
It most definitely dissolves fiberglass tanks but not aluminum or Proseal
See Rotax fuel tank and engine instructions.
My left tank has only had mogas E10 in it except for a few trips to OSH and I do not see any
deterioration in tank sealant.

There is still an obsession about Ethanol and non ethanol.
Ethanol is your octane booster in 91 E10 so leave it alone.
There remains a difference between 100 Octane and 91 Octane and you cannot just wish it away but you can certainly adapt
your installation and operating procedure to accept the lower octane fuel with very many positive results.

Most of the mogas users started their experimentation by filling one tank with mogas and the other with avgas.
Testing at altitude and observing engine instrumentation after switching tanks seems like a responsible way to go.
Every engine installation is a bit different and in a nutshell, to make good use of mogas your engine and especially your fuel system
should run as cool as possible.
Proceed with caution.
 
airguy said:
I've been doing both of those things for 8 1/2 years and 1700 operational hours, no problems yet. When do they start?
Click to expand...
To be fair, you have a return-line based, high-pressure system with components that differ substantially from much of the installed base around here. I am curious what caused the stir with Andair valves, as it's such a simple component that should have been using compatible O-rings to resist chemical attack. We've all been using E10 in our cars for 20 years...

That being said, are there any cautions about E10 in a standard Vans "tractor valve", as unfortunately that's what my plane is equipped with, and changing it out is not at the top of the to-do list. I'm guessing the fuel pump and servo have EtOH-compatible parts but can't prove it. For now I'm buying non-ethanol gas.

EDIT: Vapor pressure and vapor lock is my big concern. Hot starts in this thing are absolutely terrible compared with the IO-360 172s I've used in the past.
 
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Sam Buchanan said:
You are not under any regulatory restrictions that prevent you from using any fuel you wish. Many RVs have been flown with auto fuel for the past few decades. There are operational considerations in regard to various seasonal blends of auto gas and specific engine configurations but these don't fall under any FARs.

Also, your POH does not carry any regulatory weight since a POH is not required for aircraft with an experimental airworthiness certificate and not part of the airworthiness process.
Click to expand...
Sure?
Check your Operating Limitations, a lot of them refer to compliance with 91.9 which refers to a manual, markings, placards etc. If you have a Manual it needs to be changed, and the placards need to be changed too. Since its in 91.9 it is indeed regulatory and falls under that FAR.

Until those markings placards etc are changed you cannot use any fuel you wish because that fuel does not match your manual and placards.

Not sure what the obsession with marking "100LL only", unless it is the only per the Lycoming manual. The only requirement is to mark the minimum grade required fuel, and if per the Lycoming manual for your model it is anything other than 100LL say 93, then mark it as Min Grade 93. See 23.1557. For reference the Lycoming manual does not approve "oxygenates" at any level that would allow 10% ethanol pump gas. If you are concerned about misfuelling putting Min Grade 93 you can put NO ETHANOL as well. Nobody is keeping you from using ethanol pump gas either, but not being the builder, you probably don't know if the entire system was made compatible, so best to avoid it.
 
Sam Buchanan said:
Yes, I'm sure.
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From modern Ops Limitations

13. This aircraft must contain the placards or markings, as required by FAR 91.9. In addition, the placards and markings must be inspected for legibility and clarity, and the associated systems inspected for easy access and operation, to ensure they function as intended by the amateur builder/owner during each condition inspection.

From that, yes you are limited and under regulatory restrictions (contrary to your opinion), until your aircraft complies with 91.9.
OP stated POH and Placards say 100LL only! He does in fact have regulatory restrictions as it currently sits unless he has ancient Ops Limitations that do not reference 91.9.
 
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Why can’t the owner edit the POH (or discard it as not needed) and change his placard?
The owner would want to make a log book entry documenting the change.
 
Fred S and I were testing morgas with the water test tube method and the water soluble food coloring method years ago and never found any alcohol in the gas.
fred uses premium , me 50/50 in one tank, regular gas with MMO in cruise tank. no lead in the plugs golden brown.
P1000410.jpeg
 
turbo said:
Fred S and I were testing morgas with the water test tube method and the water soluble food coloring method years ago and never found any alcohol in the gas.
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The placard wording on fuel pumps says "maximum 10% ethanol" to which most of us assume it is 10% ethanol. A farmer friend who tests the level fairly often for the fuel in his machinery tells me the highest he has tested and found is 5.50% and the lowest being zero.

Having a Rotax 912iS (that prefers 91 octane mogas) as a powerplant I have two 10.5 gallon Fast-Flo containers that I take to Southern States Co-op and fill each with 6 gallons of 90 octane ethanol free gasoline and the remaining volume with 4.5 gallons of 93 octane 10% ethanol. This blend gives me a bit over 91 octane and the one time I stopped by the farm to have it be tested (by someone that knows how) the blend had just under 1% ethanol.

Rambling on, I know, but the point is that the mogas has less ethanol than we think.
 
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Steve Iacoviello said:
Why can’t the owner edit the POH (or discard it as not needed) and change his placard?
The owner would want to make a log book entry documenting the change.
Click to expand...

That is exactly the point I and other posters are making. There is nothing sacred about the POH, you aren't even required to have one. Peel off the tank decal and tear out the page in the POH. Suggested tank decal; "Minimum Fuel Required---Yes"..........
 
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These guys have been flying for more than a decade on pure ethanol for the most part when available with little modification to their Lycomings.

I am not a fan of ethanol but its here to stay for a few decades, so deal with it and make the best of it.
It does contribute to a very clean engine and plugs for one thing and I have yet to find a downside.
If you are looking for a legal blessing or whatever assurances you are hoping for, they don't exist and Lycoming has not approved the use of
ethanol and probably never will. Your best bet is to find someone who has been using 91 E10, talk to them and see how they are dealing with it.
We enjoy the privileges of experimental aviation and are given a wide berth when it comes to tinkering with our machines.
It does not mean that we should flagrantly through caution into the wind. Trying something that has worked well for hundreds of us
barely qualifies for experimenting, except for the fact that most of our Rvs have a slightly unique fuel system and require a bit of testing before
adding a new sticker to your fuel tank.
I did not invent any part of whats installed in my engine/fuel system, I just copied from those who have done it successfully for decades before me.
 
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