In Saskatchewan our "regular" fuel now contains 10% Ethanol. Like all alcohol, ethanol is hygroscopic, meaning it likes water and attracts moisture from the air. For the normal daily driver vehicle this is not a problem as the fuel is consumed and replaced within a week.

A vehicle that sits for extended periods may have problems. Once the ethanol has absorbed .5% water (much less when colder than 70 degrees F) the ethanol and water mix separate and drop out of suspension in the gasoline. This water ethanol mix is then drawn into the fuel system and the engine will run poorly or not at all. The remaining gasoline was formulated to utilize the higher octane rating of the ethanol and without it the octane level is reduced. This fuel may then cause pinging and engine knock on some engines.

Ethanol is also a powerful solvent and can dissolve gum and varnish in the fuel system as well as rubber and plastic.

Our normally low relative humidity in most years may not give us the problems others have had but that was not the case for the Sask. boating industry in 2007. The introduction of ethanol fuels had an immediate effect. Many boat tanks had a build up of residual water and a fresh fill of ethanol fuel and the resulting fuel separation caused havoc. Continued use of ethanol on older boats will also dissolve the fiberglass  fuel tanks. Many marinas now sell only premium gas which does not contain ethanol (yet).

If fuel is uncontaminated by water it will be clear and you should be able to read a newspaper through a glass jar of it. Water contaminated fuel will be white or milky.

Older rubber fuel lines  become soft and mushy and require replacement.