First load of mogas

jmaynard

jmaynard

Cleared for Takeoff
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Fairmont, Minnesota
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Jay Maynard
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I've got 69.6 hours on my O-200. The POH spends a page on reprinting Continental's dire warnings about mogas, then on the next page starts off with "This airplane is approved for automotive gasoline". I've decided that I have no problem with the idea of running mogas in it. The question now is: how?

Do I need to be careful about doing it the first time? Can I mix it with 100LL? I know it needs to have zero ethanol; is it safe to assume that anything I get at an airport's mogas pump will qualify? What other gotchas do I need to pay attention to, since I'll likely be using both mogas and 100LL in the airplane at different times?
 
jmaynard said:
I know it needs to have zero ethanol; is it safe to assume that anything I get at an airport's mogas pump will qualify?
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NO!

I have seen reports of gas coming out pumps labeled 'no ethanol' that does have it.

You need to test for it!

http://www.pilotsofamerica.com/forum/showpost.php?p=217134&postcount=20

This is a pic of Tony testing the gas at 6Y9 last year
attachment.php
 
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its really easy to test for ethanol.

start with a container (pop bottle etc.) with some water in it. mark the line.

fill it with gas, shake it up.

note if the line of water moved. if there was an apparent increase in the water content, you have ethanol.
 
jmaynard said:
Do I need to be careful about doing it the first time? Can I mix it with 100LL? I know it needs to have zero ethanol; is it safe to assume that anything I get at an airport's mogas pump will qualify? What other gotchas do I need to pay attention to, since I'll likely be using both mogas and 100LL in the airplane at different times?
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No.
Yes.
Probably but test it anyway. It isn't that hard.
Nothing really. Keep an eye on your quick drains. You may need to replace the seals in them.
 
jmaynard said:
How come? (Aside from possibly getting some ethanol, that is.)
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SAE Article: Surface Corrosion in Ethanol Fuel Pumps

Catastrophic failures of fuel pumps used to transport ethanol have occurred in various facilities. Failures occurred in as little as 50 hours on pumps with a 2000-hour life expectancy. Post-failure inspection of the pumps showed corrosive pitting of the metal in the areas of sliding contact. Several potential causes, including cavitation, thermal expansion of pump parts, and fuel contaminants such as acetic acid were ruled out. Fuel samples from facilities with high pump failure rates passed all D 4806 specification tests for fuel-grade ethanol, including titratable acid by D 1613. However, pH readings as low as 2.0 indicated potentially corrosive fuels. Controlled tests on pumps and corrosion tests showed that pump failures correlated with fuel pH. Corrosive fuels were found to contain ethyl sulfate, which correlated with fuel pH. It appears that ethyl sulfate originates from sulfur dioxide, which is used as an antioxidant and antiseptic in the production of ethanol.
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That puts the ph level down around that of Coca-Cola and lemon juice.
 
tonycondon said:
its really easy to test for ethanol.

start with a container (pop bottle etc.) with some water in it....
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Pop bottle? Way overkill. I went to the local hobby store and bought three test tubes for $5. I bought a squeeze-bulb tool for adding water to batteries for another $5 or so. Takes me about a minute or less to test a load before dumping it in the tank.

Testing process graphically illustrated on Page 7 of this EAA Chapter 26 Newsletter. EAA sells a nice test kit for $15.

Do NOT trust any labels on the fuel pumps, or what the minimum-wage attendants may tell you. Test every load.

Ron Wanttaja
 
wanttaja said:
Pop bottle? Way overkill. I went to the local hobby store and bought three test tubes for $5. I bought a squeeze-bulb tool for adding water to batteries for another $5 or so. Takes me about a minute or less to test a load before dumping it in the tank.

Ron Wanttaja
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Pop bottle is FREE. :yes: And if you use a liter sized pop bottle, you need nothing else. You get the whole kit (one liter sized pop bottle) for no initial investment. (FREE). :rofl:

TEST EVERY LOAD. Labels can lie.
 
jmaynard said:
How come? (Aside from possibly getting some ethanol, that is.)
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Well, it has been my experience that if anything is affected by the change from 100LL to mogas, it will be the seals in the quick drains. In the 25 or so years that I have used Mogas, that is the only issue I have ever had.
 
A skinny and tall shaped container works better for the water test for alcohol. A plastic drink bottle is kinda large and wastes too much gasoline.

A 1:3 ratio of 100LL to (alcohol-free) mogas gives pretty much the ideal fuel for low-compression Lycs and Conts. That way, you've got just enough tetraethyl lead in the mix to benefit the valves but not so much that it leaves heavy deposits like straight 100LL does.

My 150hp Cherokee loves mogas and I often run mixes ranging from 1:3 to half & half. The only caveat is that when it's really super hot OAT (like 100+ deg F or higher), the mogas does have a noticeable tendency to want to vapor-lock immediately after engine shutdown on the ground when I restart it before giving it time to cool down, and because of that, I'll run closer to straight 100LL in the hot Texas summertime.
 
Neal Howard said:
A skinny and tall shaped container works better for the water test for alcohol. A plastic drink bottle is kinda large and wastes too much gasoline.
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If you are careful, you can decant the gasoline and put it into the tank. I find it harder to use a test tube arrangement at the gas pump, where you SHOULD be doing the test.
 
I'm working on something simple and cheap that you has a wide enough opening for a pump nozzle and with a little valve in the bottom so you can simply and easily drain out the water. Right now I have about 10 used 16 oz drinking water bottles (and the number is growing) with little holes in the bottom (punched with an awl) for draining the water. I leave them in the sun to evap the gas so I can recycle them. One handly reusable unit is my goal and when I get it together I'll let you all know.
 
Plastic rain gauge works perfectly. It's already graduated too. $2.79 at Lowes.
 
Greg Bockelman said:
If you are careful, you can decant the gasoline and put it into the tank. I find it harder to use a test tube arrangement at the gas pump, where you SHOULD be doing the test.
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Don't know why. If I find the load of gas in my two 2.5 gallon cans has ethanol, it'll just go in my car instead. I don't have to keep a sealed container to haul my test kit to the gas station, and (especially) I don't have to answer any questions about what I'm doing. I don't really want the owner of the gas station to know I'm putting it in an airplane....

Ron Wanttaja
 
wanttaja said:
I don't have to keep a sealed container to haul my test kit to the gas station, and (especially) I don't have to answer any questions about what I'm doing. I don't really want the owner of the gas station to know I'm putting it in an airplane....

Ron Wanttaja
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Sealed container? And why would the owner of the station care?

But bottom line is, Whatever works for you. :)
 
Greg Bockelman said:
Sealed container? And why would the owner of the station care?
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Because some business owners are irrational about selling anything for use in aircraft due to perceived liability issues. For instance, I had a auto/truck brake-relining shop refuse to sell me brake-pad material when I told them it was for an airplane. They were OK when I changed my story to "an Off-Road Vehicle."

I've had two other instances with similar reactions, so I prefer to not attract attention....

Ron Wanttaja
 
wanttaja said:
Because some business owners are irrational about selling anything for use in aircraft due to perceived liability issues. For instance, I had a auto/truck brake-relining shop refuse to sell me brake-pad material when I told them it was for an airplane. They were OK when I changed my story to "an Off-Road Vehicle."

I've had two other instances with similar reactions, so I prefer to not attract attention....

Ron Wanttaja
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That is valid.

How did you go about cutting the brake material?
 
Neal Howard said:
A 1:3 ratio of 100LL to (alcohol-free) mogas gives pretty much the ideal fuel for low-compression Lycs and Conts. That way, you've got just enough tetraethyl lead in the mix to benefit the valves but not so much that it leaves heavy deposits like straight 100LL does.
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Really? What beneficial effect does TEL have on the valves?

Jim
 
Greg Bockelman said:
Wow. The stuff I got was so hard that it wore out a bandsaw blade with just one pad. I ended up having them waterjet cut and even that wasn't the best.

Where did you get the material?
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IIRC, I found the place in the Yellow Pages by looking under "brake service" and looking for places that did stuff like commercial trucks.

My bandsaw is a Delta 3-wheel model, running at about 1500 fpm with a metal-cutting blade (e.g., aluminum-cutting speeds). Final smoothing was with an ordinary benchtop belt sander.

I made a dozen or so one afternoon with no difficulty. Worked fine over the years, but finally replaced them with brand-new Barry Jay sets last year.

This was the outer pad, only ~3/8" thick, not the real fat one that sits atop the hydraulic ram on the brake.

Ron Wanttaja
 
They look just like mine. I didn't check dimensions. I have enough now to last probably my lifetime, but time will tell just how they hold up.
 
weirdjim said:
Really? What beneficial effect does TEL have on the valves?

Jim
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The valve seat and face need some lead in air-cooled aircraft engines that do not have valves and seats made specifically to operate on unleaded gasoline. The EAA published an article not too many years ago describing how older design aircraft engines can suffer early valve & seat damage when broken-in and run on a 100% lead-free diet and how the very same engines after an overhaul can run cleaner and last longer when run on a mostly lead-free diet with initial break-in on leaded fuel and subsequent occasional operation on fuel with small amounts of lead in it. I have faith that the EAA's experts know what they're talking about in that article too.
 
Neal Howard said:
The valve seat and face need some lead in air-cooled aircraft engines that do not have valves and seats made specifically to operate on unleaded gasoline. The EAA published an article not too many years ago describing how older design aircraft engines can suffer early valve & seat damage when broken-in and run on a 100% lead-free diet and how the very same engines after an overhaul can run cleaner and last longer when run on a mostly lead-free diet with initial break-in on leaded fuel and subsequent occasional operation on fuel with small amounts of lead in it. I have faith that the EAA's experts know what they're talking about in that article too.
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When I bought my Fly Baby, the Continental C-85 had about 25 hours SMOH. I ran car gas exclusively, and at the first annual (~45 hours later) I had an exhaust valve leaking. The local cylinder specialist basically echoed EAA's advice; that I should be operating this engine on leaded fuel for the first 50 hours or so to build up some lead on the valves and seats. I went to exclusively 100LL for the next year, then went to a 3-fills autogas/1 fill 100LL schedule that has worked well since.

Ron Wanttaja
 
Neal Howard said:
The valve seat and face need some lead in air-cooled aircraft engines that do not have valves and seats made specifically to operate on unleaded gasoline. The EAA published an article not too many years ago describing how older design aircraft engines can suffer early valve & seat damage when broken-in and run on a 100% lead-free diet and how the very same engines after an overhaul can run cleaner and last longer when run on a mostly lead-free diet with initial break-in on leaded fuel and subsequent occasional operation on fuel with small amounts of lead in it. I have faith that the EAA's experts know what they're talking about in that article too.
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That's an interesting heresy, in that older engines designed to run on 80/87 had zero lead content in their fuel for the most part. The specification was 0.5 ml tel/Gallon but that was the MAX. Most gasoline supplied under the 80/87 specification had zero. So from the late 40s through the mid-80s, our low-compression engines were running, essentially, on unleaded.

It is amazing that so many engines ran for so long without the slightest trace of lead in their combustion chambers.

I'm not going to argue that a few microns of lead on the valve stems isn't going to hurt that engine and may in fact be a bit beneficial, but running a mixture of 100LL and unleaded for the life of the engine is an absolute crock of crap.

So you plate out a few microns of lead on the valve stems in the first ten or twenty hours. Good idea, actually. However, running more LL through the system plates out a few more microns, then a mil or two and pretty soon you've got a hung valve on lead. It ain't a pretty sight.

Yeah, both EAA and AvWeb suggest the first few hours on LL, but from then on, unleaded only.

Jim
 
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