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Old 07-03-2018, 06:43 PM
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bryanflood bryanflood is offline
Join Date: Aug 2006
Posts: 109
Default A gas contaminated with jet a

So today I had less than a cup of jet a mixed into one of my tanks of 16 gallons of 100ll on accident when someone grabbed the wrong fuel hose. The pump was not on but there was residual fuel in the nozzle. Surprisingly they seemed to completely mix and not separate. I always thought that jet fuel would separate out but the mechnic at the field said that jet-a and 100ll mix. Weird, does anyone have an idea what to do with this? if I have to dump 16 gallons of 100ll gas, where does it go? My guess is the engine wouldn't even notice this small amount of jet a, anyone had experience with this? I'm sure lycoming has a bulletin advising what to do?

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Old 07-03-2018, 06:51 PM
74-07 74-07 is offline
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Location: Greenville, SC
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Default Jet A

Fuel contamination is fuel contamination. There is no published data anywhere that I know of that allows jet A mixed with 100ll to be used by a piston engine. For what it's worth, I would, without hesitation, drain that entire tank and refill with 100ll. As for disposal, a call to your local fuel supplier would probably get you the answer. Alternatively, let your lawnmower decide if it likes the mixture. A failure there will result in a unmowed lawn rather than an unplanned arrival on top of someone's BMW.

Last edited by 74-07 : 07-03-2018 at 06:55 PM.
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Old 07-03-2018, 06:57 PM
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ColoCardinal ColoCardinal is offline
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Default 100LL/Jet A mix

Your lawnmower, 65 Mustang and a whole host of other engines will love you for bringing it home.
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Old 07-03-2018, 07:01 PM
Aluminum Aluminum is offline
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Dump it and flush the entire fuel system before starting engine, or you will need to have the engine taken apart. Kerosene contamination claimed many lives--almost got Bob Hoover.
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Old 07-03-2018, 07:05 PM
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One of the big fuel suppliers bought a lot of brand new engines in NorCal somewhere around the late 80s or early 90s for failures due to Jet A getting into the 100LL supply chain.

IIRC, couple crashes also happened-----not sure about any fatalities.

Drain it would be my choice.
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Old 07-03-2018, 07:06 PM
BobTurner BobTurner is offline
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Location: Livermore, CA
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Understand the danger: Jet A has essentially zero anti-knock properties (e.g., very low "Octane number"). Engines run on substantial amounts (how large is substantial? I don't know) detonate severely, with the typical failure mode being melting a hole thru the aluminum piston, about 1/2 mile from the takeoff runway.
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Old 07-03-2018, 08:00 PM
xblueh2o xblueh2o is offline
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Drain it. Don't use it in your airplane. Don't even think about it.

AvGas and Jet A will mix very easily with no easy way to tell without letting it sit for hours or days.
To test for the presence of Jet A in AvGas there are a couple simple things you can do.
1. Smell it. AvGas should smell like, well, AvGas. It shouldn't smell like kerosene.
2. Pour some on a piece of paper. If it is all AvGas it will evaporate and leave the paper completely dry (possibly dyed blue and a little wrinkled but you get the idea). If there is turbine fuel the paper will never dry completely out because turbine fuel will leave a little ring of oil stain wetness on the paper.
Since you know for certain that this one tank is contaminated it will be simple to drain and flush.

Yep, back in the mid 90s a major oil company had a mishap and sent Jet A contaminated 100LL all over Northern Ca. They did the right thing and bought hundreds of new engines including a complete set of four for a B-17. No surprise that about 10 years later the same company announced they were getting out of the AvGas business.
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Old 07-03-2018, 08:32 PM
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Vlad Vlad is offline
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Once upon a time far away from home I borrowed several jar cans to get to the village only gas pump. The jars were used for diesel fuel and were supposedly empty. I caught it timely and managed to dump the diesel ( a quart total) before filling them up. Still had some mix up engine told me that. Drain it and use elsewhere.
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Old 07-03-2018, 09:19 PM
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Walt Walt is offline
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Just curious, lots of folks advocate using Marvel "Mystery" oil (mineral spirits mostly) in their fuel, so why would a cup of Marvel be ok but a cup of Jet A (kerosene) will definately kill you?
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Old 07-03-2018, 09:48 PM
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DanH DanH is offline
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A full cup in 16 gallons is 1/256, or about 4 tenths of a percent. It would be interesting to conduct the standard field test for jet fuel contamination of avgas. Place a few drops of a sample on a white piece of paper and allow to evaporate. An oily ring evident after evaporation indicates jet or diesel, while an unmarked paper indicates a clean avgas sample.

Is 4/10's of one percent detectable?
Dan Horton
Barrett IO-390
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