Yellow fuel in sump

AuntPeggy

Final Approach
PoA Supporter
Joined
May 23, 2006
Messages
8,479
Location
Oklahoma
Display Name

Display name:
Namaste
The C-172 has not been getting enough exercise lately. The other night, Hubby took it up for its first launch since the annual in May. The fuel tests for both wings looked normal and blue, but the one under the belly returned what looked like yellow fuel. A second sample was the same. He eventually removed about a pint of the wrong colored stuff before getting blue fuel.

Any idea what turns the fuel (100LL) yellow?

Interesting side note: He was there with an old friend who is in the habit of simply pulling the knob and discharging some fuel from the gascolator without capturing it into a jar to test. If it had been his airplane, he would not have known that it was the wrong color.
 
Did someone pee in your gas tank?
 
Did you save it to see if it is even fuel. 100LL evaporates without a residue, while water would not evaporate quickly. I use a GATTS and this supposedly will allow the fuel to pass throught the filter, but not water, but to be perfectly honest, if I got a pint of something out of my gas tank that I could not identify and assure it was safe to fly I would scrub the flight until I had a mechanic check it out.
 
Isn't diesel fuel from a car gas station yellow? Or maybe E85? I know I've seen yellow fuel somewhere before...
 
Whatever it is, it is contamination if all you burn is 100LL.
 
Isn't diesel fuel from a car gas station yellow? Or maybe E85? I know I've seen yellow fuel somewhere before...

Yep, yellow for road diesel. Off- road diesel is red.
 
Sometimes old auto fuel can look kinda yellow? What did it smell and feel like?
 
Could it have picked up a little color from rubber hoses attached to the gascolator?
 
JetA is also yellow or straw color.

Did someone put a little JetA in your tank and not tell you. Since it's heavier, it would sink to the lowest point. I have seen that happen more times than I'd like to admit.
 
Jet-A is yellow(ish). I'm thinking that is what it is. Can't find the specific gravity of 100LL, but I think Jet-A is heavier. A sniff test would have been of value. Jet-A has a distinct odor even when mixed with 100ll. It would also have a more "oily" feel than straight 100LL. How it got there I wouldn't want to guess, but I've seen the mixture ruin engines.
 
JetA is also yellow or straw color.

Did someone put a little JetA in your tank and not tell you. Since it's heavier, it would sink to the lowest point. I have seen that happen more times than I'd like to admit.

I'm surprised that it doesn't just mix in - like oil added to gas for a two stroke.
 
Carnac the Magnificent says:

You replaced a fuel line during your annual.

Is he correct?

If so, that's what's turning your fuel a funny color. Give it some time for whatever causes the color change to leach out of the hose, and you'll get your normal blue back.

No impact to engine ops or safety.

(Happened to me this year after adding a fuel flow sensor and replacing the line it spliced into. Spooked me a little until I remembered reading messages on other forums before about folks who had replaced fuel lines and were similarly surprised.)

Edit: See attached file for more info on this phenomenon.
 

Attachments

  • 802.pdf
    132.5 KB · Views: 47
Last edited:
SG:

Gasoline: 0.73
Jet-a (Kerosene): 0.82

www.engineeringtoolbox.com is your friend.

Jim

Maybe. Maybe not. Just a few weeks ago I was reviewing the chapter on properties of solutions in Pauling's descriptive "Chemistry" text and he states:
"Substance vary greatly in their solubilities in various solvents. There are a few general rules about solubility, which, however, apply in the main to organic compounds.

One of these rules is that a substance tends to dissolve in solvents that are chemically similar to it. For example, the hydrocarbon naphthalene, C10H8, has a high solubility in gasoline, which is a mixture of hydrocarbons; it has a somewhat smaller solubility in ethyl alcohol, C2H5OH, whose molecules consist of short hydrocarbon chains with hydroxide groups attached, and a very small solubility in water, which is much different from a hydrocarbon."
 

One of these rules is that a substance tends to dissolve in solvents that are chemically similar to it.

That's what I would expect, and have seen happen with gasoline and diesel fuel. It mixes and stays mixed.

The Jet-A I'm familiar with is clear, not yellow.

Dan
 
Maybe. Maybe not.."


There is no "maybe, maybe not" THe OP asked what the specfic gravity of two substances were and I posted them. Whether or not they are miscible is a totally different question.

And whether or not they STAY miscible over hours, days, weeks, or months is another totally different question.

Jim
 
There is no "maybe, maybe not" THe OP asked what the specfic gravity of two substances were and I posted them. Whether or not they are miscible is a totally different question.

And whether or not they STAY miscible over hours, days, weeks, or months is another totally different question.

Jim

They are miscible and will stay miscible. It's possible they weren't well mixed allowing the heavier jet-a to be removed before the two fuels diffused into one another.
 
There is no "maybe, maybe not" THe OP asked what the specfic gravity of two substances were and I posted them. Whether or not they are miscible is a totally different question.

And whether or not they STAY miscible over hours, days, weeks, or months is another totally different question.

Jim

Sorry, I incorrectly quoted your post when I should have quoted post 10 in my "maybe, maybe not" reply. I quoted your post only because it appeared to be the most recent in the subthread about Jet-A and 100LL mixing vs separating. Your post was of course a proper answer to the question.
 
JetA is also yellow or straw color.

Did someone put a little JetA in your tank and not tell you. Since it's heavier, it would sink to the lowest point. I have seen that happen more times than I'd like to admit.
Jet wouldn't evaporate either once it was sumped. And it's clear, at least if it's proper JetA it's clear. If you touch JetA it's very oily and you won't be able to get dry whatever you touched it with, your shirt/gloves/pants will stay damp from it. It's nothing like 100LL where it evaporates and you don't notice it. The stuff will stink up a whole load of clothes if you wash them together.
I'm surprised that it doesn't just mix in - like oil added to gas for a two stroke.

No, it wouldn't. JetA is kerosene based and it weighs 6.7 pounds (on average) per gallon compared to 100LL's 6 pounds per gallon. They're very different fuels and I really don't think they'd ever blend together.
 
Jet wouldn't evaporate either once it was sumped. And it's clear, at least if it's proper JetA it's clear. If you touch JetA it's very oily and you won't be able to get dry whatever you touched it with, your shirt/gloves/pants will stay damp from it. It's nothing like 100LL where it evaporates and you don't notice it. The stuff will stink up a whole load of clothes if you wash them together.


No, it wouldn't. JetA is kerosene based and it weighs 6.7 pounds (on average) per gallon compared to 100LL's 6 pounds per gallon. They're very different fuels and I really don't think they'd ever blend together.

If not caught, they could blend together given time or mixing such as in turbulence. Both are hydrocarbon based fuels and are fully soluble in each other. As you note, jet A does evaporate more slowly and one can place a drop on a piece of paper ans see if it evaporates or stays oily.

Glad the water was found on the ground.
 
No, it wouldn't. JetA is kerosene based and it weighs 6.7 pounds (on average) per gallon compared to 100LL's 6 pounds per gallon. They're very different fuels and I really don't think they'd ever blend together.

Someone needs to try it. They're both hydrocarbon liquids, like gasoline and two-stroke oil, which blend just fine and stay that way despite having different specific gravities. We're not talking hydrocarbon liquids and water here.

Dan
 
If not caught, they could blend together given time or mixing such as in turbulence. Both are hydrocarbon based fuels and are fully soluble in each other. As you note, jet A does evaporate more slowly and one can place a drop on a piece of paper ans see if it evaporates or stays oily.

Glad the water was found on the ground.

I guess no one remembers the mis-fueling that occurred in So-Cal a few years back.

5% Jet "A" in 100LL caused many engines to get overhauled on the truck companies dime.
there is an AD on it.
 
I've seen the results of someone misfueling a Navajo many years ago. The Jet-A destroyed the engines. The feds brought some of the parts to a meeting. They were a total mess. Oh, and the Navajo was also destroyed in an emergency landing. Pilot survived.
 
I'd be mighty tempted to drain the tank, toss the fuel (at my club, they'd probably burn it in the snowblower or the tugs), and fuel with known good fuel (partially fill, wouldn't fill it until satisified it was the fuel and not something else).

I hope it's just water, like you suspect.
 
Interesting that it happened right after annual. You sure there were no fuel hoses replaced?
 
Interesting that it happened right after annual. You sure there were no fuel hoses replaced?

Yes. Pretty benign annual. Hubby always assists, so we know what goes in/out.
 
Back
Top