Old Fuel

[loansharkblv]

At what stage is fuel old? Days / weeks / months?

If you have a small amount of fuel 1/3 tanks that has been standing for 3 months does adding new fuel sort out the old stuff?

I have been told that old fuel smells terrible but without ever smelling it I am unsure…...

[Morph]

Do you pre-mix or not?

My understanding is that the octane in fuel reduces fairly rapidly when you have pre-mixed. However there are guys at our airfield who fly once every 4 to 5 months and the plane starts and runs fine. Whether the power is at the same level I wouldn't know. My gut feel is the fuel will also be richer, as the fuel component will evaporate before the two-stroke oil. Also, if the plane has been standing for a long time with a fairly empty tank, and there has been changes in humidity you stand the risk of water in the fuel. Always drain a little fuel from the bottom of the tank to check for water.

Also check your float-chambers for a white powdery residue that starts to build up when the plane stands for too long. It tends to collect under the floats, as the fuel level starts to evaporate and where the floats eventually make contact with the fuel bowl. A quick look will not show it, you have to remove the floats. I found it in both my float chambers under the floats. It's like an oxidation and requires quite a bit of scraping to get rid of it.

Additionally, planes that stand for long periods of time are subject to corrosion inside the motor. If your plane tends to stand idle then before you store it, use the choke/enricher to kill the motor instead of using the mag switches. This will pump a large fuel/oil mixture into the motor which will help in keeping it lubricated over longer periods.

Adding fresh fuel will help to dilute the old stale stuff. Obviously it would be best to replace it, but that is not always feasible. If there is 5 liters left and you put 25 liter of fresh stuff in you will not notice much difference.

[loansharkblv]

"Morpheus"

Do you pre-mix or not?
If your plane tends to stand idle then before you store it, use the choke/enricher to kill the motor instead of using the mag switches.

Sounds like good advice - At this stage I am getting out once every two weeks or so but will remember this for those windy months.