Backcountry Pilot

[TexasNick offline]

Split from Filling Gas Cans because it has turned into another ethanol discussion.
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Don't take the ethanol out of the car gas because that will seriously decrease the octane level of the end product.

best thing to do is test your gas with a test tube or olive bottle (instructions for home made version can be found online) and fill it with a little water, add the car gas to the bottle, then shake and check and see if that water level increases in your bottle--if it does, then you have ethanol in the fuel.

Avgas in my area is $4.55....ridiculous..does not make fun flying anymore. However, ethanol-free gas is just $2.38. What a difference! I bought the EAA STC* and am now using car gas for the time being. I know that it won't be like this forever as all gas stations are required to have ethanol in the fuel by the end of next year.
* the EAA STC comes with documentation about a study done in the 1980s of autogas vs avgas and they found that a C150 on pipeline patrol for 1 year had more efficiency and better engine power with the cargas vs the avgas.

[dirtstrip offline]

There is a newer avgas V auto gas report by EAA from 2007 and should be read by anyone switching to auto gas. Results can vary from airframe type to airframe type even though the engines themselves my respond just fine.

http://www.eaa.org/autofuel/autogas/art ... 0Avgas.pdf

[EZFlap offline]

Don't take the ethanol out of the car gas because that will seriously decrease the octane level of the end product.

best thing to do is test your gas with a test tube or olive bottle ....

Yes, I know all about that. It is exactly what I would do on a larger scale to get the water and alcohol out.

My best info so far is that if you start out with 91 octane premium car gas, and take the ethanol out, you wind up with something like 85 or 87 octane. My engine is certified on 73 octane.

[dirtstrip offline]

If an aircraft engine is certified for 73 octane. Add about 5 octane to the automobile octane number to make the two equal. Auto gas would need to be rated at 78 octane to be apples to apples equal against 73 on the aircraft fuel. The two octane rating systems are different. The difference is explained in the article I quoted above.

[hotrod180 offline]

Eric, are you taking the alcohol out of the car gas, or are you able to buy it without alcohol? Do you get the varnish and yellow goop buildup in your fuel system, or does the car gas burn clean? ..............

I'm still able to buy ethanol-free car gas locally at at least one station. How long that'll last- who knows?
No varnish, no goop, no fouled or dirty plugs, no clinkers on the plugs....all in all, no problems due to car gas use. Over 250 hours on this one (320 Lyc) and about 1700 on the last one (C-145 Continental).
I would think twice before "washing" the ethanol out of gasohol, unless you have a way of testing the octane afterward or know FOR SURE the rating of the fuel before they contaminated it with ethanol.

Eric

[EZFlap offline]

Thanks for the verification of no problems Hotrod. It's an old 172/ Cont. O-300 I'm flying behind also, low compression for sure.

I'm far far from an expert on octane, but it would seem reasonable to me that taking out ethanol would not lower the octane THAT bad. If it would, then all that car gas for all those years before ethanol would have been too low of an octane?

Unfortunately California is adding ethanol probably more than anyone. I just got some no-ethanol car gas in Arizona a week ago, but it was only the 91 premium gas. The station owner said that both of the other grades had ethanol in it.

[hotrod180 offline]

..............
I'm far far from an expert on octane, but it would seem reasonable to me that taking out ethanol would not lower the octane THAT bad. If it would, then all that car gas for all those years before ethanol would have been too low of an octane?............

No, when the fuel is intended to be ethanolized, they start out with sub-octane gas then add ethanol to get back up to the desired octane (87,89, or 91). So if you suck the ethanol out, you end up with the original sub-octane blend.

[180Marty offline]

Here in NW Iowa 87 octane straight unleaded is the lowest grade we have. It is pipelined up to Sioux City and a few more terminals in the area. The 10% ethanol is added and the 87 becomes 89 or 89.5 octane. Not sure why the .5 octane difference at different stations. I remember reading that in eastern Iowa a few years back they were getting 85 octane and making it 87 by adding 10% ethanol. Anyway, 10% ethanol adds 2 to 2.5 octane points,20% would add 4 to 5, 30% 6 to 7.5. I had a shop in Omaha take my Marvel MA4-5 carburetor apart after 2 years of 10% ethanol auto fuel use. I didn't tell them what I'd been doing when I asked how it looked inside-----the answer was "very good".

[180Marty offline]

EZFlap, When you rig up your tank to remove the ethanol, you should build a still and get it back to 190 proof. You could then sell it to someone with a flex fuel vehicle. Here is a link to PlanetE85 where there is a youtube of a guy with a sensor in his car to tell ethanol %.

http://e85vehicles.com/e85/index.php/to ... l#msg22101

[MtCoyote offline]

"My best info so far is that if you start out with 91 octane premium car gas, and take the ethanol out, you wind up with something like 85 or 87 octane."

How is it that the local Kicks 66 station, alcohol free Premium gas is still rated at 91 Octane. All of our base stock gas is the same. It all comes into Boise in the pipeline. At the distribution point, the rack, where the trucks load out of, is where the alcohol is added along with the additives.

[Jaerl offline]

Can someone explain why the ethanol is bad? The only real reason I can see for not using it in aircraft is because the water that would be separated and drained out the sumps would now be suspended in the fuel. This could cause more Carburetor Icing. Anyone know of any other physical reasons not to use it?

I use Mogas exclusively in my 150 unless I am away from home. I had Blackstone Labs do the oil test on my 150 at the last oil change. They told me the engine looked great and said if I would quit using Avgas completely, they would be able to monitor the bearing wear. They test thousands of samples and if they suggest using straight Mogas, that is enough for me. If I were to leave the planes sitting for a long time I would fill them with avgas I think most varnish you get is from the additives left from evaporation. I understand that Avgas has no additives.

I test the fuel I buy here in Utah and I haven't found any ethanol yet. I also heard the Idaho will not put it in Premium so that Airctraft can continue to use it. That sounds like a great idea.

[hotrod180 offline]

Can someone explain why the ethanol is bad? The only real reason I can see for not using it in aircraft is because the water that would be separated and drained out the sumps would now be suspended in the fuel. This could cause more Carburetor Icing. Anyone know of any other physical reasons not to use it? .......

My concern is that #1, ethanol is reputed to be corrosive, & may attack fuel system components (rubber seals, aluminum lines, etc), and #2, if affinity for water. Maybe get a big slug of all that water suspended in the fuel attached to the ethanol all at once- not good. More likely to me is that the ethanol will bond to the water in the fuel, then get drained out along with it when sumping the tanks, resulting in sub-octane fuel.
Maybe it is no bi deal, but I know the original Cessna TCDS for my airplane sez no alcohol, & the EAA STC paperwork sez max 3% (I think). So unless they change their tune, thanks anyways but I'll pass on the ethanol.

Eric

[Jaerl offline]

Hey Eric

Everything you said makes sense. I haven't used ethanol yet and hopefully I won't have to. I didn't have any paperwork, just stickers, for the Mogas STC on my 150 so I bought another one. The guy at Peterson's asked me if I really wanted one since all fuel will have ethanol soon. Is ethanol going to be required by the fun hating government or can gas companies decide what to do?

I found this on the web.

In the case of four-stroke engines, the water-ethanol phase may
combust in the engine. This combustion can be damaging to the
engine because the water ethanol phase creates a leaner
combustion mixture (i.e. air to fuel ratio is higher than ideal).
Leaner mixtures tend to combust at higher temperatures, and can
damage engines, particularly those without sensors to calibrate
air to fuel ratios.

Here is the whole paper: http://www.epa.gov/otaq/regs/fuels/rfg/waterphs.pdf

[180Marty offline]

More likely to me is that the ethanol will bond to the water in the fuel, then get drained out along with it when sumping the tanks, resulting in sub-octane fuel.

Putting a plastic baggy over the vent with a bread wrapper tie snugging it(kinda like a pitot cover), when sitting in the hangar, seems to keep the water out of the fuel to begin with. Also, putting fresh fuel in just before flight, like Rotax suggests, seems to be working.

[Jaerl offline]

Here is another quote fron the paper I quoted before:

"Since ethanol and water readily dissolve in each other, when
ethanol is used as an additive in gasoline, water will actually
dissolve in the blended fuel to a much greater extent than in
conventional gasoline. When the water reaches the maximum amount
that the gasoline blend can dissolve, any additional water will
separate from the gasoline."

Just like air can only hold so much water till it starts raining, fuel can hold so much water until saturated. Then the excess will end up in the sumps to be drained out. There is still water in the fuel and with Ethanol it is a higher percentage. The higher the temprature the more water will be suspended in the fuel. Something to think about.

[EZFlap offline]

My limited understanding is that ethanol (alcohol) attacks aluminum and rubber. Both of which are important parts of the airplane fuel system. Most people agree that the alcohol will not destroy anything overnight, but most of the people directly involved in the auto gas STC research say it is no good for airplanes.

Also, having ethanol in the gas would invalidate any autogas STC, which would immediately invalidate your insurance.

The airport where I'm based at has a 5+ mile zone of major city/houses.buildings in most directions, no less than that before you get out into the desert or the mountains to the north and east. 25-40 miles in the other direction (across LA main metro area). So anything that has a potential effect on reliability or could cause unwanted silence in the airplane is a big deal.

Around here, any time an airplane lands somewhere off-airport, the rotary wing news vermin start circling within 10 minutes, followed closely by the FAA, followed by some little putz city attorney looking for camera time, followed by Gloria Allred looking for a deep pocket, followed by Al Sharpton looking for a race war, etc. etc. etc.

Suffice to say I want the off-airport landings to be at MY discretion, not the raghead at the gas station.

[WWhunter offline]

Bill,
I have a 1960 172 with an O-300 and have been burning auto fuel almost exclusively for over 20 years. Same goes for my Champ. I would guess somewhere's in all those years I have inadvertently poured in some gas with ethanol. I have never had any problems. The only thing that might have been related to it was needing to replace the O-ring in my primer. But that was the first time in all my years of ownership so there is no way of telling if it was from the auto fuel. I honestly believe that my O-300 has fewer problems with auto fuel than I had running 100LL. With 100LL I would need to clean the plugs at every 25 hour oil change. If I didn't I would start having a plug lead up and lose performance. I would also have to lean the carb upon starting and be quite vigilant on the mixture control while on extended flights otherwise I would experience sputtering. Maybe it is all in my head but I sure haven't seemed to have the issue since burning mostly auto gas. I occasionally put in 100LL to keep the valves lubricated.
Here in MN the premium gas at MOST stations is ethanol free. Maybe you should try and get a grass-roots project started to allow the same thing isw Ca. Here it is labeled for collector cars, tractors, snowmobiles, lawnmowers etc. Go get the Hot-Rodders involved...lots of those in Ca.
WW

[hicountry offline]

Bill,
I have a 1960 172 with an O-300 and have been burning auto fuel almost exclusively for over 20 years. Same goes for my Champ. I would guess somewhere's in all those years I have inadvertently poured in some gas with ethanol. I have never had any problems. The only thing that might have been related to it was needing to replace the O-ring in my primer. But that was the first time in all my years of ownership so there is no way of telling if it was from the auto fuel. I honestly believe that my O-300 has fewer problems with auto fuel than I had running 100LL. With 100LL I would need to clean the plugs at every 25 hour oil change. If I didn't I would start having a plug lead up and lose performance. I would also have to lean the carb upon starting and be quite vigilant on the mixture control while on extended flights otherwise I would experience sputtering. Maybe it is all in my head but I sure haven't seemed to have the issue since burning mostly auto gas. I occasionally put in 100LL to keep the valves lubricated.
Here in MN the premium gas at MOST stations is ethanol free. Maybe you should try and get a grass-roots project started to allow the same thing isw Ca. Here it is labeled for collector cars, tractors, snowmobiles, lawnmowers etc. Go get the Hot-Rodders involved...lots of those in Ca.
WW

WWhunter...try about 4oz of Marvel Mystery Oil in the fuel tank for every 10 gal 100LL. This would really help in my 170 with the lead fouling. Could go 100 hrs or annual with very little lead fouling. I still use MM Oil in my 360 and I burn 50% 100LL and 50% 91 Oct car gas. HC

[TexasNick offline]

I believe Marvel M is not legal. You can get a legal version which is FAA approved at:
http://www.alcorinc.com/fuel-treatment/alcor-tcp.php

I think if you crash, insurance won't cover your expenses if they find the MM stuff in there.

That's IF you have insurance

[edleg offline]

Don't a great many aircraft in Brazil run on some mixture of alcohol.... all the way up to 100% ethanol?

I believe their (Brazil) ag planes run on alcohol and I thought I read somewhere that Cessna was shipping aircraft to Brazil to run on ethanol.

What is the difference between 100% and 10% alcohol as far as the corrosive problems, vapor lock, etc?

Do a google search on aircraft engines, Brazil and alcohol and see what comes up.