What is “stale” fuel, and should I use it?
“Stale” fuel is caused by improper storage, and usually smells sour. The gasoline has been allowed to get warm, thus catalysing olefin decomposition reactions, and perhaps also losing volatile material in unsealed containers. Such fuel will tend to rapidly form gums, and will usually have a significant reduction in octane rating. The fuel can be used by blending with twice the volume of new gasoline. Some stale fuels can drop several octane numbers, so be generous with the dilution.
