A gas contaminated with jet a

[RV12JT]

What I?d like to know...Who screwed up in the first place?

[Phil]

When I was a kid, I accidentally topped off our Chevy suburban with diesel and we ran it out of the tank. The thing ran horribly, but it ran well enough to get us home and to run the tank dry on a country road before we put in regular fuel and brought it home.

What we discovered was a little surprising and that is much of the diesel ended up in the oil. Since it didn't burn as fast as the gasoline in the mix, the gas would ignite raising the pressures in the cylinder to drive the piston down, and the pressures were high enough to drive the unburned diesel down past the rings where it collected into the sump. When you'd drain the oil, you'd drain diesel and then oil (I think that was the order).

It took a number of oil changes to get through that tank

Ultimately we had to overhaul the engine later on down the road, because diesel doesn't lubricate quite as well oil and our wear rate was accelerated during the time the diesel ended up in the oil.

So even a little bit of diesel, while it may not affect the combustion inside the cylinder, could find its way past the rings, into the oil, where there could be other consequences that go beyond 'its ability to run'.

Phil

[Pallet]

Anyone have a little time on their hands? Put some 100LL in a clear jug and put a small measured of jet A and mix. let it set a couple days and take a picture for us. See if it mixes. I'm guessing it does. Any takers? I would like to know. You can't tell me this hasn't happened before to a lot of pilots.

[TimO]

Todd, I was just thinking the same thing. While I totally agree with the people that say drain the tank, I also totally agree with the others that noted that the percentage of fuel is very very small. It's not as in the mis-fueling incidents. This is a very small amount. I have kerosene and 100LL on hand, along with jars, at my hangar. When I'm out there again I'll mix 50/50 and see what happens over a couple weeks.

[KnotKrazy]

I'm not a petro engineer, so I cannot make a knowledgable comment on the effect. I do know this however: it's not worth my life to find out, even in the long run. I would always harbor a slight suspicion towards the motor as to whether or not the jet fuel had some detrimental effect that may or may not surface at a later time. Like right after takeoff in a densely populated area.
Just adding my two cents, not making assertions to the decision of the owner. YMMV.

[johnbright]

Originally Posted by Phil

When I was a kid, I accidentally topped off our Chevy suburban with diesel and we ran it out of the tank. The thing ran horribly, but it ran well enough to get us home and to run the tank dry on a country road before we put in regular fuel and brought it home.

What we discovered was a little surprising and that is much of the diesel ended up in the oil. Since it didn't burn as fast as the gasoline in the mix, the gas would ignite raising the pressures in the cylinder to drive the piston down, and the pressures were high enough to drive the unburned diesel down past the rings where it collected into the sump. When you'd drain the oil, you'd drain diesel and then oil (I think that was the order).

It took a number of oil changes to get through that tank

Ultimately we had to overhaul the engine later on down the road, because diesel doesn't lubricate quite as well oil and our wear rate was accelerated during the time the diesel ended up in the oil.

So even a little bit of diesel, while it may not affect the combustion inside the cylinder, could find its way past the rings, into the oil, where there could be other consequences that go beyond 'its ability to run'.

Phil

I had the same experience with an automotive engine. IMO conservative assumption is you're putting that cup of jet fuel kerosene into the crankcase.

[TimO]

18 hours after mixing 100LL and Kerosene. Zero separation. It's been kept very stable, with no vibrations or disturbances.

[bryanflood]

Well,

Thanks for all the advice. Last night i drained the tank containing the one cup of jet-a. There was no evidence of separation in the drained fuel. I also performed the paper test on the drained sample and some pure 100ll out of the other tank. There was no difference between the two, niether left stains on the paper. I even took the paper out into direct sunlight and looked through a magnifying glass. As far as i could tell the 1 cup of jet-a was totally undetectable by these methods. My own opinion is that i could have used the fuel in the plane safely, especially in cruse flight where the effective compression is lower. However, since my opinion is based on assumptions not testing i have refueled the plane with fresh 100ll.

I would be interested to figure out how the jet-a in such a low concentration affects the octane. I think it would also be interesting to learn more about how much marvels mystery oil people are running in their fuel, might have similar properties.

Thanks,

Bryan

[Sam Buchanan]

Originally Posted by bryanflood

I would be interested to figure out how the jet-a in such a low concentration affects the octane. I think it would also be interesting to learn more about how much marvels mystery oil people are running in their fuel, might have similar properties.

Thanks,

Bryan

The bottle of MMO that I have recommends 4oz per 10gal of gas. Sounds like that is close to what you had in your tank.

[lr172]

Originally Posted by bryanflood

I would be interested to figure out how the jet-a in such a low concentration affects the octane.

Thanks,

Bryan

someone posted this on your thread. 2% Jet A mixed with 100LL drops your octane rating 1 point. Most standard compression Lycomings require an octane rating several points below 100.

Larry