When avgas turns yellow

Yellow avgas from the gascolator the other day. Plane had been sitting for a while. Drained it until fresh blue came through.

What does this color change represent? Is the fuel bad? Also curious about fuel laying in the hose from the fuel tank. Neighbor says he pumps it back into the supply tank and proceeds to fill the plane from there.

Watched a separate neighbor put a nice Cub into the trees last summer due to bad fuel so this issue is living at the forefront of my aviation concerns.

I've never seen that.....

Possibly it was just water? Ever had mogas in it? Was there anything (debris) in the gascolator?

Who peed in your fuel tank??

I've seen avgas turn yellow-ish in two circumstances:

1) Some auto gas mixed in

2) Wrong kind of rubber hoses used in fuel system. At least, that's what I was told by the mechanic. Changed hoses and never happened again. I have no idea what "wrong kind" it was.

MTV

Checking the gascolator next. There is a chance that water was in there, the cover over the nose tank cap blew away. (Tcart) Mechanic showed me that someone was using air hose for fuel line and changed it out.

Water or mogas.

Time for a Mr. Funnel.

I've never seen yellow from mogas or water. My bet would be a hose getting gummy.

Glenn

I share a 1000 gallon tank with another guy. We started getting discolored fuel, more brown looking than yellow. Fuel in both tank filters was blue. I replaced the fuel hose and problem solved. The hose was old....too old I guess.

Slightly off topic but related to fuel hoses. Annual inspection a few years back I noted that the fire sleeve on a fuel line forward of the firewall was turning black. No obvious cause. I pulled the fuel line, split the fire sleeve and it was black inside. I wiped the sleeve and hose with a white rag and it turned blue. It wasn’t black but very dark blue. I rigged a cap for one end of the fuel line and a connection on the other end to hook up to my air compressor. I dropped the hose into a tank of water and turned on the air. The hose looked like a bubbler in an aquarium, bubbles from everywhere! I replaced all the rubber fuel lines figuring if one was rotten the rest were probably in similar condition. No discolored fuel in that case because all rotten lines were downstream of all drain points.

666 Teflon hose is the only safe option

Glenn

Water and rust, possibly from a rust gas storage can/drum?