Lawnmower Fuel Issues – Ethanol & Storage

Many people are using gas for their lawnmowers that contains around 10% ethanol.  Ethanol blended fuel is commonly used as an alternative to unleaded fuel. If you are switching to gas it contains ethanol, check your lawn mowers manufacturer’s recommendations on any adjustments that may be required to carburetor.

A common problem with ethanol blended gas is that the piston ring may start sticking after a long period of use. This may occur because gas with 10% ethanol has a higher water absorption rate, and can attract water, which can reduce lubrication and allow rubber gaskets and hoses to dry out.  The alcohol results in a phase separation occurring in the fuel.

At the end of your lawnmowers season, you should ensure your lawnmowers fuel tank is empty. For lawn mowers that use unleaded gas, you can add a stabilizer to it, to keep the fuel ready for next season. However, ethanol blended fuel has much less of a shelf life than regular gasoline. Its maximum shelf life is only 90 days, which means it’s less stable, so to be safe you should replace this type of fuel every 2 to 4 weeks while your lawnmower is in use.

 As a general rule of thumb, you always want to store your lawnmower in a dry well covered place. This is even more important if you are using ethanol blended fuel, because you need to ensure additional water/moisture does not come in contact with this gas.  As a caution against water contamination of the fuel, you should ensure the octane level is over 90, because the water can dilute the ethanol blended fuel dropping its octane level by as much as three points.

When using ethanol blended fuel make sure you don’t put any additional additives or treatment products for fuel system into the tank, because most of those things also contain alcohol.

It is also worth noting that ethanol blended gas can reduce the fuel efficiency by anywhere between 2 to 40%, resulting in lower gas mileage.

When you are using ethanol blended fuel, you must ensure that you store it in dry, clean tanks that are alcohol resistant. To know if the fuel has gone bad, you can look to see if the gases become layered. If water contamination or phase separation has occurred, you will be able to see two or three different layers in the fuel. There is nothing you can do at this point to restore the fuel, it would have to be properly disposed of.

Knowing these lawn mower fuel issues, relating to ethanol & storage, you can take proper care of your lawn mower and possibly still use ethanol blended fuel.  However, you should read your lawn mowers owner’s manual to ensure that ethanol blended gas is suitable for your particular model. It is worth noting that any engine, whether it be in a car or a lawnmower, that is older than 1998 will generally not allow for this type of fuel to be used. Doing so can invite damage to the engine’s parts and performance issues for the machinery.  Always check your facts first.