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Fuel storage

tomkk

Well Known Member
This must have been discussed before but I'll be darned if I could find the thread. Anyway, the storage life of avgas is pretty long (~ a year) and ethanol auto fuel is short (~ small number of weeks) but what about ethanol free 93 octane auto fuel? Long, short or somewhere in the middle?
 
Longest I?ve gone, is a month due to weather, on 91 no ethanol fuel. Ran like a top. If it went longer, than say, 2 months, I?d probably mix in a little 100LL.
 
Low Octane

As I understand it the problem with Auto Fuel, both Ethanol and Non-Ethanol alike, is that it loses Octane fairly quickly. Low octane can and most likely will cause detonation, which will destroy a piston in very short order. I believe that the Octane begins to significantly degrade around 8 weeks. The problem is that you have no idea how long it has been sitting in the storage tanks before you buy it from the gas station. So if it has a been a month before using the auto fuel I would drain it and put it in your car and get fresh fuel to run in your airplane.
 
In both my suby powered RV 4 and grumman yankee with auto fuel sts I used small amount marvel mystery oil an stabilizor all time!
 
I store 93 mogas with ethanol in 5 gallon cans , sealed is best for you don't want the exposure to air, this prevents oxidation and the gas will keep for months. Rotate your supply every few months, if it last that long. I do have a 50+ gallon tank I use to fuel the plane for convenience, but that gas goes quickly.
Been doing this for a few years and have over 400 hours on my Rotax 912 in an S7s with no issues. I'd use non ethanol if it was available cuz itll last even longer, over a year from what I've read
 
I just burned 13-year old avgas in my Cessna 150. No problems at all. Mixed 50/50 with new avgas. FWIW
 
As I understand it the problem with Auto Fuel, both Ethanol and Non-Ethanol alike, is that it loses Octane fairly quickly. Low octane can and most likely will cause detonation, which will destroy a piston in very short order. I believe that the Octane begins to significantly degrade around 8 weeks. The problem is that you have no idea how long it has been sitting in the storage tanks before you buy it from the gas station. So if it has a been a month before using the auto fuel I would drain it and put it in your car and get fresh fuel to run in your airplane.

I don't have much to add to the conversation on when fuel goes bad. However, with regards to aging in tanks, I used to work at a relatively low volume convenience store and we still got trucks at least once a week; a busier store might be every other day. Point being I don't think you need to worry about how long it's been sitting at the station. If however you're talking about a tank on the airport or your own bulk tank that may be another story.
 
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