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Fuel consumption  

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mfullmer
(@mfullmer)
Active Member

Greetings;

We bought our 108-1 last summer. So far, I've been running 100LL with TCP. From what most experts are saying, unleaded fuel is the key to long life for our Franklin engines. Swift UL94 is only available at one airport in Michigan, and it's 111 miles away. Clearly that's not practical. I contacted Swift about buying a few drums directly from them. With shipping costs, it worked out to $5.98/gal. OUCH! I'm currently scouting for sources of ethanol-free mogas nearby. If I can figure out the logistics of transporting, storing, filling, etc., this may be the way to go.

Can anyone tell me if there's a difference in fuel consumption with a 90 octane mogas vs 100LL avgas? Thanks in advance.

Mark and Julie Fullmer'47 108-1 N8368K

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Posted : 11/02/2019 7:40 pm
Stinsono
(@stinsono)
Member Admin

I found this handy site with ethanol free gas station locations

https://www.pure-gas.org

Sent from my iPhone using Tapatalk

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Posted : 11/02/2019 7:45 pm
lawheelock
(@lawheelock)
Honorable Member

A Stinson F150 burns an average of 10 gal/hr no matter what fuel you are using. This is based on operating a F150 for more than 40 years and more than 3500 hours at altitudes from sea level to 12,000 ft. Above 10,000 ft I was able to get consumption to a little under 9 gal per hour but how much time does one spend at 10,000 ft in a Stinson? This is based on 80/87 avgas when it was available, 100LL, 87 octane mogas, and 93 octane mogas.
If you are not burning 10 gal per hour, you are running your engine too slow and you will have increased maintenance.
An F 165 burns about the same even though it runs faster, but the higher lift valves let it breath a little more efficiently.. They have the same compression ratio and the same displacement which are the main factors in fuel consumption.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

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Posted : 11/02/2019 10:53 pm
lawheelock
(@lawheelock)
Honorable Member

Please use caution in using the pure gas site to find ethanol free mogas.
Many of the station listings have not been updated for 3 or 4 years.
As an example, I found a couple of years ago that my Murphy station that I had bought fuel from for years suddenly had an ethanol sticker on the pumps. I tested the fuel and the ethanol content was about 5%.
So, if you find a station advertised as having ethanol free gas for your Stinson, get a small amount of it and test it for ethanol. If it is dispensed in the same hose as fuel containing ethanol, run enough through it before sampling to remove any ethanol containing fuel in the hose and plumbing.
Franklin F150 and F165 engines run much better and never foul plugs with lead if operated totally on ethanol free mogas. The engines never need lead as the valve seats are hardened and do not need lead for preventing recession.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

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Posted : 11/02/2019 11:06 pm
mfullmer
(@mfullmer)
Active Member

Thanks, Larry. I knew I could count on you for an authoritative response.

Mark and Julie Fullmer'47 108-1 N8368K

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Posted : 11/02/2019 11:08 pm
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