Any octane of gasoline available at your regional filling station should work fine in your lawnmower, As long as you prevent the diesel section. High-octanes will not necessarily enhance your lawnmower’s performance, but they won’t damage the engine. A larger concern is to watch for the amount of ethanol present in the gasoline. This number should be uploaded on the front of the gasoline pump. Lawnmower needs to 10% ethanol material in the gas. Any more than that can cause corrosion as the ethanol absorbs water from the air.