Auto Gas & Engines

[Mongo]

I work in Indy Car racing, and we race with 95% ethanol, 5% is gasoline just so we lush racers don't drink it as cheap booze.
The only major changes we've made was to Kalrez o-rings and sock filters (as used in street cars) in the fuel cell. We(the entire series)have never had a single issue with water in the fuel, but we only let the fuel sit in a fuel tank for one week, any longer than that and it is removed and placed back in the fuel drum, as it is hydroscopic. If the fuel is stored properly in an air tight container when not in use for extended periods of time, you will have no issues with water.
We also have no issues with vapor lock but we run a system similar to dry sump oiling, so the main pickup is always submerged and under 5psi.
We run a return-less fuel injection system, the same as in on newer cars, and it is a closed loop sequential system using two Lambda sensors.

The only thing I would be concerned with is rapid pressure and temperature changes, which aircraft experience, this would need some testing.

[Tyler]

Here is the Marathon website and their Wholesale products list. I looked and they don't have any gas stations in the 25 mile radius of Seattle but that doesn't mean that there isn't a marina that won't let you fill up a couple of gas cans or a truck tank.

[TwinPOS]

After getting a huge chunk of info and doing some math, I run 100LL through my Stinson, quite frankly car gas vs av fuel not half as good, the time it takes for it to break down while sitting, the QC, etc, etc.

If you're running a lawnmower engine, or a rotax or a subaru engine, or one of those half VW units, then it might not be as bad, just seems like a cheap way to make a expensive problem in a certified AC

This has not been my experience at all. Ethanol free auto fuel in my area is over 2.00 per gallon cheaper. That savings paid for an engine on my old 182, and has been keeping my current airplane running flawlessly for over 1200 hrs. My plugs are cleaner, and compressions mid 70's. The savings based on a 2000hr. TBO, more than pay for a lot of GA planes purchase price. I agree that it is not a good idea to leave it sitting in the plane for a long period of time. I believe that to be true of a lot of fuels, 100ll not withstanding. I don't have much experience with Stinsons, but I have heard that the Franklins (150-165) do better on a mogas diet. What engine do you have and what QC problems have you encountered?

[hotrod150]

....We know ethinol will seperate if mixed with water, so what's the chances of figuring a method of removing the stuff?? Maybe even a big can to mix a larger quantity of water with Auto gas then simply siphen the fuel off the top after a period of settlement time....

This has been discussed extensively on one of the sites I'm on, don't recall if it was thois one or not. Ethanol, despite having less energy per gallon than clear gas, is an octane booster. So if you shake the ethanol out, you'll end up with an octane level somewhat less than the label sez. It could be that 91 or 92 octane E10 would still be 87-ish octane after ethanol removal, but no way to test that I know of. Besides, if you burn enough fuel to make it a worthwhile endeavor, the actual removal process becomes a helluva big job. I fly about 160 hours a year, which works out to an average of about 13 hours a month-- at 8.5 gph, that's about 120 gallons to de-ethanolize to end up with the required 110 gallons of clear gas, AND about 10 gallons of ethanol to get rid of.

[hotrod150]

.....quite frankly car gas vs av fuel not half as good, the time it takes for it to break down while sitting, the QC, etc, etc. ....

I disagree. In my experience, other than the recent ethanol issue, using car gas has almost no down side. Clean plugs with no lead fouling, and even now saves me about $1.50 a gallon ($13 an hour) in fuel costs. In the past, the savings have been as high as $2 a gallon or even somewhat more. I fly often enough that the gas doesn't sit in the tanks long enough to go flat. Regarding quality control, of course you have to keep an eye on what you put in the tanks-- I've seen some recent quality issues with both mogas & 100LL sold at a local airport.
But if 100LL works better for you than mogas,then by all means use it & more power to you.

[Vick]

After getting a huge chunk of info and doing some math, I run 100LL through my Stinson, quite frankly car gas vs av fuel not half as good, the time it takes for it to break down while sitting, the QC, etc, etc.

What engine do you have in your Stinson? If it's a Franklin you might want to do more homework on the question - Franklins were designed to burn unleaded fuel. Unless you are adding something like TCP to 100LL, you are asking for valve trouble. (Clean) Mogas is unquestionably the preferred fuel for Franklins, the lower cost is just a benefit. If you live somewhere where ethanol is mandated, you get the pleasure of paying for 100LL plus whatever additive you choose to scavenge the lead.

[bush master]

vick,

You stated that the Franklin was designed for unleaded fuel, have you seen this in any of the specifications? I have had people of the 40s tell me av fuel had no lead and it was said during that period not use auto fuel because it had lead in it. Have you or anyone else heard this?

[PilotRPI]

I found some Jabiru documentation that says not to use over 10% ethanol in their engines. Seems they might be in the same league as Rotax (fuel wise). If you go into a project knowing that you are planning on using E10 in your plane, would it be that much harder to plan ahead by using stainless steel lines and Viton-B in place of rubber in the fuel system? Sounds like there are even options to remove water (strainer socks). What I end up with would be experimental, so no biggie if it is not technically certified.

[hotrod150]

You stated that the Franklin was designed for unleaded fuel, have you seen this in any of the specifications? I have had people of the 40s tell me av fuel had no lead and it was said during that period not use auto fuel because it had lead in it. Have you or anyone else heard this?

I believe 100LL has 2 grams of lead per gallon, the old 80/87 avgas had 1/2 gram of lead per gallon. To come close to duplicating 80/87, mix 1 gallon 100LL with 3 gallons unleaded e-zero 87 octane car gas-- this is what Petersen recommends for radial engines BTW, and what I did myself for years. I finally just went to 100% car gas, with an occasional shot of 100LL on trips when cargas isn't available.
Petersen does list a 87 octane mogas STC for the 150 horse & 165 horse Franklin's. Nothing shown for the 220 Franklin, apparently a 100LL only show due to the higher compression. But as mentiond, EAA & Petersen STC's both say no ethanol, so unless the ethanol train deails we've all be stuck with 100LL-- or it's no doubt more expensive replacement.

[RDUStinson]

You stated that the Franklin was designed for unleaded fuel, have you seen this in any of the specifications? I have had people of the 40s tell me av fuel had no lead and it was said during that period not use auto fuel because it had lead in it. Have you or anyone else heard this?

The type certificate for both the airframe and engine specify "80/87 aviation gasoline"- this is also reflected in the Petersen STC. Like you I've heard from some of the older fellas that there was no lead in 80/87 back then.

All the reputable Franklin builders I've ever talked to say that lead is nothing but bad for the Franklin. They have hardened (stellite) valve seats so they don't need the lubrication, and they tend to stick or burn valves and foul plugs if fed a steady diet of 100LL.

At my home field we have great prices on 100LL, and it's only about $0.55 more than car gas, but I will go to great lengths to find clear car gas, which is getting more and more difficult.

[Terry]

All the reputable Franklin builders I've ever talked to say that lead is nothing but bad for the Franklin. They have hardened (stellite) valve seats so they don't need the lubrication, and they tend to stick or burn valves and foul plugs if fed a steady diet of 100LL.

I can vouch for all three, not necessarily in that order
Heavy on lean and TCP if burning 100ll in your Frank.

[Vick]

Hotrod brings up an important distinction, I should have said that mogas is the preferred fuel for the 150 & 165 Franks. I don't have any experience with the 220s but I imagine they would do fine on 100LL due to the high compression. Hopefully Mountain Matt will weigh in with his experience with his 220.