I once stored 5 gallons of premixed 2 cycle oil in regular pump gasohol in a portable sealed plastic outboard fuel tank for 5 years without problems. I used it in my trimmer/chainsaw, etc. without issue. Long ago I read that 2 cycle oil will stabilize gasohol. A sealed container prevents moisture from being drawn in as the fuel expands and contracts with minor temperature changes. Sealed containers must have the pressure/vacuum relieved with significant changes in temperature to prevent damage to the container. High humidity air is worse when drawn into the tank and causes water to condense when it cools. Ethanol can absorb about 1/2% water before the alcohol/water mixture separates from the gas and settles to the bottom of the tank. This causes a number of problems and should be avoided. The alcohol that separates from the gasoline causes a lean mixture if the engine will run at all, and microbes can grow in the mixture, causing corrosion of metal and debris to form. Be sure the vacuum/pressure valve on the tank fuel cap is working properly, if utilized on your cap (like on a car). Close the manual vent on caps that have them when the mower is not in use. Monitor the sealed tank for excessive pressure/vacuum buildup with significant temperature changes, and vent the tank momentarily if needed, as with seasonal changes.
When I use an outboard motor, I disconnect the hose from the tank when I return from a trip and let the engine run until the carbs run dry, which kills the engine. With no fuel left to evaporate in the bowls and leave gum deposits, I've not had a problem w/ the carbs sitting over a number of years. If your mower has a manual fuel shut off valve, close it and run the carb dry before storing it. If it doesn't, add one, or I suppose if your mower has a solenoid fuel shutoff valve, you could disconnect the wire at the valve, or put a switch inline with the wire, to switch it off to run the carb dry. Ethanol is a good cleaner of gum and varnish deposits if it is suspended in the gas, as it should be.
Fuel de-icer contains alcohol, often methanol, and will absorb water if there is too much in the fuel tank. It takes only a few drops of water in a carb bowl to wreak havoc. Drain the bowl into a container if water is suspected, and look for water. If the fuel filter is transparent, look for water separation in the bottom of the filter.
When I use an outboard motor, I disconnect the hose from the tank when I return from a trip and let the engine run until the carbs run dry, which kills the engine. With no fuel left to evaporate in the bowls and leave gum deposits, I've not had a problem w/ the carbs sitting over a number of years. If your mower has a manual fuel shut off valve, close it and run the carb dry before storing it. If it doesn't, add one, or I suppose if your mower has a solenoid fuel shutoff valve, you could disconnect the wire at the valve, or put a switch inline with the wire, to switch it off to run the carb dry. Ethanol is a good cleaner of gum and varnish deposits if it is suspended in the gas, as it should be.
Fuel de-icer contains alcohol, often methanol, and will absorb water if there is too much in the fuel tank. It takes only a few drops of water in a carb bowl to wreak havoc. Drain the bowl into a container if water is suspected, and look for water. If the fuel filter is transparent, look for water separation in the bottom of the filter.
