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Avgas vs Mogas

I

irishrv

I'm New Here
We are in the process of final construction of an RV7A with a 200hp fuel injected Lycoming engine (A1B6D). With the increasing price of fuel it is becoming increasingly important to try and limit fuel price within the constraints of safety. I am looking at using a 50:50 mix of AVGAS:MOGAS to run this aircraft to limit running costs. What are your views/reservations/comments on this.

Thanks
 
i think you hit the nail on the head. your engine and wallet will love it. you might even start using a stronger mix of mogas in the cruise tank as you feel better with time. 8 year satisfied user! on my second engine. first went 3,150 hours.
 
turbo said:
i think you hit the nail on the head. your engine and wallet will love it. you might even start using a stronger mix of mogas in the cruise tank as you feel better with time. 8 year satisfied user! on my second engine. first went 3,150 hours.
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Ed, are you able to get ethanol free gas, or is that something you worry about? Also, how do you tanker the fuel?

To the original poster - my concerns would be the increased possibility of vapor lock, which your installation may or may not have problems with, and the potential effects of ethanol on proseal and other non-metal items in the fuel system, if you can't get ethanol free fuel.
 
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i use regular car gas in the mix. switch over to the strong mix about 10 miles out to purge the ethanol out. 5 gal cans using one of those high tech siphoning hoses with a one way valve.
 
I run 93 octane ethanol free mogas in my right tank that I use for cruise occasionally mixing in a bit of 100LL in that tank, and use 100LL for take off and landings, which I suppose will help me with vapor lock in these hot TX days. I fly it fairly regularly. If I were to let it sit for awhile, I'd consider filling both tanks with 100LL.

Many said I’m doing my engine a favor, as well as my wallet. One guy that runs 100% mogas looks at it this way. He’s saving at least a buck a gallon, and with a 9-10 gallon per hour flow, with a 2,400 TBO, he’s saved enough to pay for a complete new engine or an excellent overhaul back to remanufactured specs that didn’t cost him a thing, other than to switch over to mogas.

You’ll want to note at least here in the states that some gas stations that claim ethanol free actually aren’t, so you’ll want to test it with your simple glass tube you can get at aircraft spruce or other suppliers.

One pleasant surprise I found was that quite a few gas stations I’ve tested that supposedly have ethanol in it, DO NOT! I think after the government quit subsidizing them, there are going to be more gas stations that are doing away with ethanol, but still haven't removed their ethanol stickers from their pumps. Even my local Sam’s here doesn’t use ethanol, but there octane rating for high grade isn’t that good. I have to shop around for 93.
 
Ethanol free

I believe the MOGAS in Ireland (Eire?), is ethanol free I think the fuel there is just lead free(on mainland UK its that way, fuel is horrendously expensive over there), I don't believe they put any fancy additives in it. But you'd need to confirm what if any additives they might use and how it will effect your engine.

There is a huge difference here between MOGAS and AVGAS prices, but finding ethanol free MOGAS here is still something I will consider when the time comes.
 
15-20 years ago, the flying club I was in used 90% mogas+10% avgas in their fleet of aircraft: J3 Cub, Aeronca Champ, Cessnas including 182s, and a Bonanza. No problems with vapor lock with the 10% avgas. This was long before ethanol of course.
 
For those considering MOGAS and looking for sources - if you live near the water or in a region with lots of recreational fishing, look for stations to cater to boaters. Often, you will find "boat gas" is zero-ethanol. It will likely be a higher priced that auto fuel with ethanol but significantly lower than AVGAS.
 
Lots of sucessful users, lots of things to watch for......

L'Avion said:
http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1070R.pdf
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so to summarize;

MO DAY YEAR MO DAY YEAR
11 09 62 04 16 12

Lycoming updates this info at least every 50 years????? :)

I can burn UL91 in my old 0-320-A, except they don't make it in North America?
..so any other fuel, 94 octane ethanol free autogas etc. is not 'certified', but I should be ok to use it, in the summer, in my aircraft, with all the 16 pages of caveats.
 
I have a vapour lock proof electric fuel pump system (two electric fuel pumps, no mechanical pump) so this may not be quite so relavent to you.

I use 100% premium autogas on an AFP FI injection system. I run lean of peak and get about 7.7GPH on a 10 ethanol blend and 160kts at altitude in an RV7a.

I am considering dropping to regular mogas but I need to do some testing before I do.

I have about 500 hours running as above.

There si a lot of discussion on running mogas in the forums.

Personally if I never put avgas in my airplane again it will be too soon.

Frank
 
They do !

The electrical fuel pumps do help in preventing vapour lock in the fuel system.
Electrical or mechanical makes no real difference except that the electrical pumps can be located in a cool spot and low in the fuel system so as not to have to draw fuel uphill. Not only is the mechanical pump located somewhat high in the fuel system but also connected to a hot engine block and effectively acting as a fuel boiler and vapour generator.
Placing fuel pumps low in the wing root or floor of the fuselage makes them push fuel up to the fuel controller and prevents vapour lock from occurring in the first place.
An additional benefit of using electrical fuel pumps would be the ethanol compatible components in the pump as opposed to the questionable rubber components in the mechanical fuel pump.
To answer the OP's question, while you are at it, use electrical pumps and the rest of the system won't care weather you burn mogas or avgas or ethanol or any mix there of.
 
Not exactly

The all electrical fuel system consists of 2 electric fuel pumps and no mechanical pump.
You'll have to design an electrical system with integrated redundancies to keep the electrons flowing.
The mechanical pump cannot be used as a back up since it cannot be shut off
and is therefore the primary pump when used with one electrical pump.
An alternative method is using avgas in one tank and mogas in the other.
Operating on avgas for take off and landing and mogas for cruise will let you keep the mechanical pump with one electric boost pump.
A small modification (return line) will help keep vapour lock at bay in all but the most extreme conditions.
This is how I fly using 91 Octane E10. I burn through about 4 tanks of mogas before filling up the other tank with avgas.
 
Can you make the mechanical pump ethanol compatible?

N427EF said:
The all electrical fuel system consists of 2 electric fuel pumps and no mechanical pump.
You'll have to design an electrical system with integrated redundancies to keep the electrons flowing.
The mechanical pump cannot be used as a back up since it cannot be shut off
and is therefore the primary pump when used with one electrical pump.
An alternative method is using avgas in one tank and mogas in the other.
Operating on avgas for take off and landing and mogas for cruise will let you keep the mechanical pump with one electric boost pump.
A small modification (return line) will help keep vapour lock at bay in all but the most extreme conditions.
This is how I fly using 91 Octane E10. I burn through about 4 tanks of mogas before filling up the other tank with avgas.
Click to expand...
 
BHunt said:
Can you make the mechanical pump ethanol compatible?
Click to expand...

No, at least not yet. Mechanical fuel pump manufacturers have thus far refused to certify ethanol compatible diaphragms for the pumps (certainly due to cost of certification).
 
Good news is not far away, relatively speaking.

Having tasted it :) I can say I am impressed, having seen the test data, I am REALLY impressed. In particular for the future of Warbirds and any big engines.

It will replace the avgas at your airfield some day soon. I can't say when, it will not be in 6 weeks, but it should not take years.

Aviation gasoline has a bright future.

And as Forrest Gump would say, That is about all I have to say about that!
 
Optimistic !

OZ,
seems that you know something we don't, although I have a pretty good idea what you are talking about.
Having observed the hipe of "new" and alternative engines as well as new and replacement fuels for the better part of the last 20 years, I would not suggest to anyone to wait for it. The certification process of a replacement fuel is moving at a glacial pace, if not slower.
To the OP, I would suggest that you set up your fuel system to be as tolerant to different fuels as you can. There is very little expense in making a few changes to your fuel system that will accommodate mogas in the future.
No matter what comes down the pike as far as aviation fuels, it'll always be much more expensive than mogas.
As far as an ethanol tolerant diaphragm in the mechanical fuel pump,
I can't tell you, but all of Brazil's GA fleet uses ethanol laced avgas
and they use the same airplanes and engine set up we use. You can draw your own conclusion as to the reliability of the mechanical fuel pump diaphragm.
 
krw5927 said:
No, at least not yet. Mechanical fuel pump manufacturers have thus far refused to certify ethanol compatible diaphragms for the pumps (certainly due to cost of certification).
Click to expand...

Call
http://www.aeroaccessories.com/fuelpumps.html

& have a conversation with them. I think that you will be pleasantly surprised.

I did, and I was.

Charlie
(of course, I don't care about any steenking 'certification')
 
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Mogas vs Avgas

I use ethanol free Mogas in the left tank and 100 low lead avgas in the right tank as many general aviation plane owner do.

1) Use the right tank (100 LL Avgas) for take off, climb and landing.

2) Use the Left tank (Mogas) for cruise.

Reason:
Saves enough annually, ($1.00 per gallon) to do an upgrade every year.

No system is perfect although this system is a compromise that saves money with out problems or worries.

Caution: 1)Make sure Mogas is ethanol free if you are concerned about it.
2) Make sure you have low compression pistons that qualify for the lower octane of Mogas.
 
NickAir said:
I use ethanol free Mogas in the left tank and 100 low lead avgas in the right tank as many general aviation plane owner do.

1) Use the right tank (100 LL Avgas) for take off, climb and landing.

2) Use the Left tank (Mogas) for cruise.

Reason:
Saves enough annually, ($1.00 per gallon) to do an upgrade every year.

No system is perfect although this system is a compromise that saves money with out problems or worries.

Caution: 1)Make sure Mogas is ethanol free if you are concerned about it.
2) Make sure you have low compression pistons that qualify for the lower octane of Mogas.
Click to expand...

What constitutes lower compression?
 
BHunt said:
What constitutes lower compression?
Click to expand...

Mattituck built my 360 with 9:1 pistons. I requested the maximum horsepower while maintaining the ability to burn 91 octane.

The phone conversation indicated that higher compression might be possible, but this would make 91 no problem.

Regards,

Scott
 
turbo said:
i use regular car gas in the mix. switch over to the strong mix about 10 miles out to purge the ethanol out. 5 gal cans using one of those high tech siphoning hoses with a one way valve.
Click to expand...

Turbo I think we are ready to start saving $$. What is the high tech siphoning devices?
Phelps
 
With Avgas now running up to $2/gallon more than premium auto fuel (with ethanol) in our area, I have been considering switching to one tank auto fuel and one tank Avgas, but a recent test result has convinced me this would not be a good idea.

According to Airflow Performance, their injection system is built for auto gas with ethanol, so no problems on that front. The electric fuel pump is also supplied by Airflow, so I assume should be compatible.

I have read elsewhere that Proseal tank sealant is compatible, so OK there.

It looks like the mechanical fuel pump may or may not be happy with ethanol - a bit of a question.

However, a spare length of fuel hose (2004 Summit Racing steel braid fuel line) placed in several inches of auto fuel with ethanol swelled up approx. 20% at the ends after 48 hours of immersion.

At some point, these hoses should be replaced anyway and its possible that newer hose would be resistant to ethanol, but for the time being, I will be sticking to Avgas.
 
dforster;(snips) It looks like the mechanical fuel pump may or may not be happy with ethanol - a bit of a question. However said:
The current mfgr of the mechanical fuel pump has told me that the diaphragm material is now compatible with ethanol (he says that they can't even purchase the old material any more). I'd suggest that anyone interested in this should contact them directly to hear it 'from the horse's mouth'.
(see post #22, this thread)

On the hose issue, I'd think that the teflon lined hose should be an option; has anyone tested it?

Charlie
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What kind of hose

(2004 Summit Racing steel braid fuel line)
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Can you be more specific?
What kind of hose are we talking about here.
Teflon hose is definitely compatible with all kinds of fuel, including ethanol contaminated mogas.
 
dforster said:
With Avgas now running up to $2/gallon more than premium auto fuel (with ethanol) in our area, I have been considering switching to one tank auto fuel and one tank Avgas, but a recent test result has convinced me this would not be a good idea.{snip}

However, a spare length of fuel hose (2004 Summit Racing steel braid fuel line) placed in several inches of auto fuel with ethanol swelled up approx. 20% at the ends after 48 hours of immersion.

At some point, these hoses should be replaced anyway and its possible that newer hose would be resistant to ethanol, but for the time being, I will be sticking to Avgas.
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Then why not consider auto fuel without the ethanol? It?s very easy to find these days. Typical savings now is often $2.00-3.00 a gallon or more over 100LL. At 8 gallons an hour burn, that's $16,000-$24,000 savings over a period of 1,000 hours.
 
wrongway john said:
Then why not consider auto fuel without the ethanol? It’s very easy to find these days. Typical savings now is often $2.00-3.00 a gallon or more over 100LL. At 8 gallons an hour burn, that's $16,000-$24,000 savings over a period of 1,000 hours.
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That would be nice, but not in CA.

EDIT!!!!! Yes, I found ethanol free gas in Redding CA 93 octane for the bargain price of...................

..... $6.92 per gallon. It makes $5.40 a gallon for 100LL look like a deal!!
 
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I am suspecting that the hose in question is teflon lined and the outer part of the hose is not ethanol compatible. Fuel comes in contact with the lining only and immersing a hose in ethanol mogas is not a realistic test.
I am hoping to hear the details about the hose.
 
gasman said:
That would be nice, but not in CA.

EDIT!!!!! Yes, I found ethanol free gas in Redding CA 93 octane for the bargain price of...................

..... $6.92 per gallon. It makes $5.40 a gallon for 100LL look like a deal!!
Click to expand...

I had no idea. Just seen 87 mogas without ethanol for $2.89 a few miles from me even though they don?t advertise it as ethanol free, it is. At another place I get the 93 mo-gas without ethanol for $3.39, but think it also went down another dime or more since I last bought it.

My airport is $4.99 a gallon for 100 LL. Most places across the US, 100 LL is over $6.00 a gallon, so you?re doing fairly good to be getting it at that price.
 
frankh said:
I have a vapour lock proof electric fuel pump system (two electric fuel pumps, no mechanical pump) so this may not be quite so relavent to you.
Click to expand...

I know with first hand experience that you can get vapor lock with a dual electric fuel pump setup! I was running ethanol free 91 pump gas (checked at each fillup) and had two different cases of vapor lock. Both times occured while running winter grade auto fuel and flying on a "hot" 70 degree January day in Kansas.

Here a link to some vapor issues of pump gas. http://www.eps-hane.com/techtips5.html
NOTE: I am not advocating the use of ethanol, just the effects reid vapor pressure (RVP) and temp info.
 
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curtis said:
I know with first hand experience that you can get vapor lock with a dual electric fuel pump setup! I was running ethanol free 91 pump gas (checked at each fillup) and had two different cases of vapor lock. Both times occured while running winter grade auto fuel and flying on a "hot" 70 degree January day in Kansas.

Here a link to some vapor issues of pump gas. http://www.eps-hane.com/techtips5.html
NOTE: I am not advocating the use of ethanol, just the effects reid vapor pressure (RVP) and temp info.
Click to expand...

I'm curious as to what kind of fuel system you have and do you have a fuel return line? The issue of mogas (with or without ethanol) has been discussed before, but I think it's the fuel delivery method that's the main issue. I've install the EFII system on my 7 (flyefii.com). I have two electric fuel pumps (one primary and one backup) and a fuel rail which feeds electronic fuel injectors that are mounted directly into the intake tubes. The fuel pump flows 30GPH and the unused fuel is returned back to the tank from which I'm drawing it from, which allows me to always have cool fresh fuel delivered to my engine. I could be wrong, but with this setup I don't see how it'll be possible to get vapor lock regardless if I'm using pure gas or gas with ethanol.
 
Sounds like a plan, I would use the food coloring method to check for ethanol as it looks to be more accurate and faster than the add water method. Just add a few drops to a clear cup of fuel and if it beads up at the bottom good, if it colors the contents not so good.
Works for me.. Walt RV-6A IO-320
 
Skeptical about the summit hose test

I'm a bit skeptical about this hose test, not that it didn't in fact swell, but that Summit primarily sells to auto enthusiasts who most likely all use fuel containing ethanol or even race fuels. If there was a severe issue I think the millions of hrs of usage the auto side sees that market would've experienced said problem first.

FWIW I use one tank Avgas and one tank ethanol free Mogas.
 
Mark33 said:
I'm curious as to what kind of fuel system you have and do you have a fuel return line?
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I have a carburetor and run Facet 40109 fuel pumps in parallel. The 40109 pumps look very similar to what Van sells, but they are internally checked.
 
Sorry for this delayed reply.

In response to an earlier posted question: The tested hose was a length left over from the original construction of the airplane, which first flew in 2005. I believe the purchase date was around 2004. This may be important, as the materials may or may not have changed during this period of time.

The box that the hose came out of was marked Aeroquip Performance Products and has a label on the side showing FCA0610. Searching this part number on the Summit Racing site comes back with this link: http://www.summitracing.com/parts/aer-fca0610 which indicates a synthetic rubber hose ". . . compatible with most fuels . . ."

Please note that this is the current description from the website. Again, I have no idea if the material might have changed in the last 8 years or so. I was surprised at the result of the test and posted the results in case others might also assume (as I did) that fuel hose from an automotive supplier would by default handle ethanol.

Perhaps it was a bad batch of hose. Maybe there is something funny about the gas sold at my local station. I don't know, but I'm glad a friend recommended the test before I put gas into the tank.
 
Thanks for posting the answer.
Your findings are a new concern for ethanol users.
I wonder how your summit racing hose is different from a teflon hose?
 
dealfair said:
Nor in Texas either.
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Depends on what part of Texas. We have many stations here in the W.Falls area that sell non-ethanol-contaminated gasoline. One of them is just a couple miles down the highway from our local airport (F14).
 
what is the max compression ratio in an o-320-e can run 90 octane, ethanol cree gas with? my engine has 9-1 pistons and i am considering replacing them with lower compression pistons.
 
Neal@F14 said:
Depends on what part of Texas. We have many stations here in the W.Falls area that sell non-ethanol-contaminated gasoline. One of them is just a couple miles down the highway from our local airport (F14).
Click to expand...

Oh really!! Well that is great news to me as there may be hope. I've complained to my legislators to at least give us a choice in the matter. I've not been able to find any from SAT south & gave up looking. I will renew my efforts & ratchet up my whining. :D

Thanks for that info & Merry Christmas to all.
 
dealfair said:
Oh really!! Well that is great news to me as there may be hope. I've complained to my legislators to at least give us a choice in the matter. I've not been able to find any from SAT south & gave up looking. I will renew my efforts & ratchet up my whining. :D

Thanks for that info & Merry Christmas to all.
Click to expand...

Hey Deal, this is your new found RV-4 flying buddy! Yes, you are correct, we need to get some mogas at both 8T6 and BEA. Did you guys get your bird put back together today? I can't wait to go flying!!
Mark
 
A question for all.

Is there a difference running 91 octane mogas in difference engines? Specifically angle valve -v- parallel valve engines?
 
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