ok, should i not be reclaiming the fuel out of the airplane after a flight, and puting it back in the fuel jug?
has turned my fuel dark. will this foul the fuel in the jug? is the fuel still good to use in the plane?
thanks for the input.

I pump it back in the jug after flying and so do all the people where I fly.

Your in-tank hardware may be corroded. If it's brass, replace it with stainless.

Good luck and regards.

I was thinking it came from the exhaust back into the airplane fuel tank. (unburned fuel?)

If you are getting dark exhaust, look for a leak from the exhaust port to the muffler. That can turn your exhaust dark. The fuel I am using is dark green, so the exhaust oil is dark anyway. I have always emptied the tank into the fuel can. Another thing that can cause dark exhaust is the gasket or shim at the back of the crankcase missing. If you use an electric starter, pushing on the prop causes the back of the crankshaft / bottom rear of the connecting rod to scrub against the back of the crankcase. Get a fresh drop of the exhaust oil on your finger, rub it gently, and look carefully. (If you had my vision, doubly carefully). If you see very tiny particles of metal, that should be your problem. Or, it could be bearing starting to go bad. Try the easy stuff first, then go deeper if you have to. Check the engine forums, there are a bunch of very experienced people in there, and some of the major manufacturers reps. But just reclaiming the fuel is not a problem.

did u unhook the exhaust hose before pumping?

Think about it this way... If you flew until the tank was empty, the fuel would go through your engine, so why not put it back in the jug?

But I don't know the reason why it's changing color. Like Mike Ledbetter, I always pump any remaining fuel back into the jug, and I think it's the most common practice. On the other hand, my fuel does not discolor. The 2nd most common practice is leaving it in the plane, but you risk the alcohol evaporating leaving fuel with very high oil content!

As it has been said above, It's a common practice to mt your
tank back to your fuel container when your done flying for the
day. I really never saw if my fuel is dis-colored?? I use power
Master fuel in a metal can.. But I never noticed any major
dis-color when mting one container to the full one. Some
members that fly alot do leave their tank as is, but they
connect the pressure and fill lines together to keep it a close
system.. Guess you could do that, if it concerns you and if
you fly often..

Mine always turns dark. I am under the impression that it is oil. The same oil that gets all over your plane.

It makes its way back to the tank through the pressure line.

Seems this should lubricate your engine ever better

Hi, I always reclaim my fuel after flying but I have a filter on the pressure line from the muffler to the tank to eliminate any foriegn particles[carbon etc] entering the fuel system.Remember you most likely have a filter on the bottom of your clunk in the fuel tank and also in your pick up line of your fuel container leading to your pump/handcrank,never had any problems with fuel discolouration.Keep it clean and it will last longer.

Good point. I always pump the gas back in using the plane's inline filter.