How do I fix a tank of Bad Gas?

Hello,

It depends on how bad the gas is contaminated. Sometimes you can add fuel additives to help minimize the contamination. You can add Heet to the fuel tank. It helps when you have water in the fuel.
But is it bad enough, then you will have to drain all the fuel out of the tank and refill with good fuel? You still want to use some fuel additives just to make sure all the components got cleaned.

Here is a helpful vide of how to drain a fuel tank:

https://youtu.be/Q5MH2gnyFH0

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.