Why is my fuel green?

JScarry

JScarry

Pre-takeoff checklist
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JScarry
My Cherokee sat since March while I tried finding an A&P to do the anuual. I finished the annual at the beginning of August and flew three times in August. Before I flew on the 31st, I filled the plane and it has been sitting on the ramp since then. Fuel color was normal.

Yesterday the fuel in the wing tanks was normal but the fuel in the gascolator was green. I did change the gasket in the gascolator during the annual but otherwise did not mess with the fuel system.

The smoke has been doing weird things to the light, but it doesn’t affect the color from the wings, just the gascolator.

I ran it for 5 minutes and the color was fine. I flew for 45 minutes and checked the gascolator again today and it looks fine.

My CFI and a mechanic are stumped. Any thoughts?


Gascolator Yesterday​
Gascolator Yesterday.jpeg

Gascolator Today
Gascolator Today.jpeg

Left Tank Yesterday
Left Tank.jpeg

Right Tank Yesterday
Right Tank.jpeg
 
Picked up some black from sitting for a long time in contact with the new gasket, were I to guess. I recall seeing similar somewhere along the way.
 
100/130 Grade Avgas was my first thought, but that looks contaminated. What’s it smell like?
 
JScarry said:
Any thoughts?
Click to expand...
Perhaps take 3 fresh samples from each wing and gascolator in separate jars and see if any color changes the next day. Or talk to the fuel distributor for ideas. I've heard of color changes before from blue to green to yellow but dont remember details.
 
That blue might be an anthraquinone dye, such as "Sudan Blue II". It turns green under acidic conditions, being at the low point is the fuel system, there may have been a little water down there. Some gascolators (really old ones) have a transparent bowl, and light could degrade the dye.
 
I seen this before when fuel has sat a long time in a belly sump or gascolator. Surprising how often fuel at the bottom of the system doesn't get thoroughly sumped to clean it out.
 
Cap'n Jack said:
That blue might be an anthraquinone dye, such as "Sudan Blue II". It turns green under acidic conditions, being at the low point is the fuel system, there may have been a little water down there. Some gascolators (really old ones) have a transparent bowl, and light could degrade the dye.
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Sounds likely. The tech spec for 100LL calls for a 1,4-dialkylanthroquinone dye of blue color, where the alkyl groups have to be large enough to confer solubility in avgas. Anthroquinone dyes are subject to oxidative degradation, which could arise from the presence of trace metal ions in water contamination in the sump. And it would take some time, which makes sense based on the length of time the sumps were left undrained. So, likely harmless unless your entire tank is green. In that case, that's what a mixture of avgas and diesel might look like. BTDT when a tankload of avgas attempted to unload through a delivery hose not cleaned out of diesel from a previous load. That was a nightmare to sort out. Fortunately, the load did not get past the test pump into a bucket. It was decidedly green, not blue, and didn't smell right.
 
Ok.. this is just plain weird. EXACTLY the same thing happened to me a few weeks ago. The plane hadn't been flown for months and was down for an extensive annual. We replaced all filters and gaskets in the fuel system including the gascolator, and serviced both fuel tanks (PA28A). When I sumped prior to the first flight, both tanks were typical 100ll blue.... And the gascolator was bright green! I just kept sumping until I got the typical blue, but got about 8 oz of the green stuff first. Neither my A&Ps nor my CFI had any idea what caused it. Looking forward to more replies. Have out 10 hours on plane since then and it's running great w no further color anomalies.

Edit... We did build and replace quite a few fuel lines, and in the process flushed them before installing them. Can't remember if it was with mineral spirits, alcohol, or something else. Any commonality there with others who've experienced the Green?
 
chemgeek said:
Sounds likely. The tech spec for 100LL calls for a 1,4-dialkylanthroquinone dye of blue color, where the alkyl groups have to be large enough to confer solubility in avgas. Anthroquinone dyes are subject to oxidative degradation, which could arise from the presence of trace metal ions in water contamination in the sump. And it would take some time, which makes sense based on the length of time the sumps were left undrained. So, likely harmless unless your entire tank is green. In that case, that's what a mixture of avgas and diesel might look like. BTDT when a tankload of avgas attempted to unload through a delivery hose not cleaned out of diesel from a previous load. That was a nightmare to sort out. Fortunately, the load did not get past the test pump into a bucket. It was decidedly green, not blue, and didn't smell right.
Click to expand...

This is exactly the sort of unintelligible gibberish that swirled through my head as I was failing Chemistry 101 in college. :D
 
Maybe it is just GREEN with envy :)
 
JScarry said:
My Cherokee sat since March while I tried finding an A&P to do the anuual. I finished the annual at the beginning of August and flew three times in August. Before I flew on the 31st, I filled the plane and it has been sitting on the ramp since then. Fuel color was normal.

Yesterday the fuel in the wing tanks was normal but the fuel in the gascolator was green. I did change the gasket in the gascolator during the annual but otherwise did not mess with the fuel system.

The smoke has been doing weird things to the light, but it doesn’t affect the color from the wings, just the gascolator.

I ran it for 5 minutes and the color was fine. I flew for 45 minutes and checked the gascolator again today and it looks fine.

My CFI and a mechanic are stumped. Any thoughts?


Gascolator Yesterday​
View attachment 90118

Gascolator Today
View attachment 90119

Left Tank Yesterday
View attachment 90116

Right Tank Yesterday
View attachment 90117
Click to expand...
I had the same issue with a new fuel hose. Something leached from the new hose to the fuel. While disconcerting, the color Change went away After a short time.
 
One reason for the dye is to tell you if a different grade of fuel has been mixed with your fuel. If a different grade was added, the color goes clear.
 
Doug Reid said:
One reason for the dye is to tell you if a different grade of fuel has been mixed with your fuel. If a different grade was added, the color goes clear.
Click to expand...
That doesn't sound right ... Is it? If I see clear.. and I have... I assume it's water and check and see if it evaporates quickly. I discovered a leaking fuel cap after sumping almost a pint of water from one tank after being parked outside in a few torrential downpours a over a matter of days. If it was mix of different fuels, I'd expect to see a bizarre color, not clear. Anyone else confirm or negate?
 
take these off

BLNDRS_NattyIceLimeX2_MClassX2_Front_1024x1024.jpg
 
MuseChaser said:
.., We did build and replace quite a few fuel lines, and in the process flushed them before installing them. Can't remember if it was with mineral spirits, alcohol, or something else. Any commonality there with others who've experienced the Green?
Click to expand...

Morgan3820 said:
I had the same issue with a new fuel hose. Something leached from the new hose to the fuel. While disconcerting, the color Change went away After a short time.
Click to expand...

Capt. Geoffrey Thorpe said:
That matches my recollection.
Click to expand...

Looks like we have an answer..."I'll take 'Fuel Hoses for $200, Alex..."
 
I've seen avgas go a little green with age. And a really slow seep from a fitting will leave a dark green oily substance behind.
 
The bowl is not glass, so a reaction with light isn’t likely. The fuel in the bowl was only in there for three weeks and since the fuel in the tanks was the right color, age isn’t a factor. Water wouldn’t affect the color and it definitely wasn’t Jet-A—no greasy residue.

I’m going to go with some kind of interaction with the new seal. Fuel shouldn’t interact with the rubber but there may have been some oil or other residue from the manufacturing process that reacted with the dye.
 
Last year annual, I had drained the fuel and the mechanic stored it in his truck mount fuel storage thing. After a long downtime for the annual, when I started pouring the gas into 1 gal buckets, the first gal was green, no one knows why. The rest were fine.
 
Doug Reid said:
One reason for the dye is to tell you if a different grade of fuel has been mixed with your fuel. If a different grade was added, the color goes clear.
Click to expand...

Your fuel will definitely not "go clear" if mixed with a different fuel. Rather the colors of the fuels will dilute each other. When diesel fuel (pale yellowish) contaminated our 100 LL load, the result was as you would expect, greenish. Not clear. JetA is clear, but if you mix that with 100LL the mixture just gets paler. The change in color due to dilution depends on the degree of contamination.
 
Just tell your friends you're using an environmentally responsible "green" fuel in your airplane now...:)
 
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