STABILIZE YOUR FUEL

 Ethanol is hydroscopic — it likes to absorb water. If water does get in, the ethanol in the gasoline will absorb it. That's acceptable with small amounts of water because it will simply be burned in the combustion cycle. But ethanol can only absorb so much water. When it becomes completely saturated, phase separation occurs, and the corrosive ethanol-water mixture sinks to the bottom of the tank. If the engine is run, this mixture can damage seals, O-rings, injectors, and other delicate engine parts. The upper "gasoline" layer will be depleted of ethanol and have a reduced octane level, which can also cause engine problems.
     If you can't empty the tank completely, then top it off and add a good fuel stabilizer. Run the engine for 10 minutes to distribute the stabilized fuel through the engine and fuel lines. Make sure the seals in the filler cap are still intact, the cap is closed tightly, and the vent for the tank is not blocked.
     Once phase separation occurs, there is no way to reverse it. No additive can rejuvenate bad gasoline. Bad fuel is bad fuel, and the only option is to dispose of it.