Fuel color on preflight sump/testing

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smoss
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Fuel color on preflight sump/testing

Post by smoss »

I had an interesting experience, and was wondering if anyone has seen similar. After my plane was sitting on a ramp in cold and rainy weather for 4 nights, while doing the preflight in very gray and overcast conditions, I drained some fuel from the left wing, and it looked what appeared to be "normal" blue with no water, then drained some from the gascolator, which looked very pale, almost clear, with no separation level, then same for the right wing--very pale with no separation level, and while it smelled like normal fuel, the scent was very light (but it was 35F out, so not much was aerosolizing.) I thought I was screwed with a ton of water that got in and drained some more from the center and right with no change. Thinking perhaps it really wasn't water, as there was no fuel/water separation at all in the tester, I then went back and drained more out of the left wing. About 5 cc more of my "normal" blue, then the remaining fuel was very pale blue, almost clear, like the other spots. Now truth be told, I don't test the fuel every time I fill up at home, so it may have been a few times since it had been drained. Started her up and she ran fine on both sides, flew home uneventfully.
Has anyone else appreciated differing levels of dye in fuel from different sources, such that it looks different on testing, or perhaps a concentration of the dye in the sump after sitting for a while? It was really low light with very cloudy skies, and in retrospect I'm not sure if the darker or the lighter blue would correspond to my "normal" in regular daylight. Both tanks had bee used on the previous flight and both tanks refilled from the same source.
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Rich
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Re: Fuel color on preflight sump/testing

Post by Rich »

Yes, I have. Fuel from the tanks is a pale blue but from the gascolator it is much deeper blue. Puzzling over this, I have been. :scratch:
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gyro3816
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Re: Fuel color on preflight sump/testing

Post by gyro3816 »

This is normal (varying levels of dye in 100LL).
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Steve
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Re: Fuel color on preflight sump/testing

Post by Steve »

It is interesting that the spec for 100LL avgas lists a maximum concentration of blue dye of 2.7 mg/l, but no minimum concentration.
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