Lawn-Boy lawnmowers that operate with a two-cycle gas-powered engine will need a combination gasoline/oil fuel. Four-cycle Lawn-Boy lawnmowers don’t require a fuel to oil ratio, or mixing of any fuels; they have a separate tank and oil pump to lubricate the crankcase. The fuel to oil ratio for two-cycle lawnmowers varies from model to model.
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Lawn-Boy lawnmowers that use two-cycle engines need a special type of oil added to the gasoline before being put in the fuel tank. This type of oil will break apart inside the gasoline and blend with the fuel. When the oil reaches the cylinder, it will be evenly distributed across the engine. These lawnmowers require two-cycle, air-cooled engine oil. Unlike automotive oil, these oils are formulated for use specifically in mixed-gas engines.
Lawn-Boy recommends using a recognized, national name-brand gasoline in its lawnmower engines. The optimum grade of gasoline for these engines is 87 octane, as anything higher will provide no benefit, and some additive packages in the higher grades may even harm the engine. Don’t use any fuel with additives, such as ethanol or gasohol, whatever the grade of gasoline. If you can’t find 87 octane in your area, use the closest to that grade of gasoline.
Those Lawn-Boy lawnmowers that use a premixed fuel will all have different mix ratio requirements. These engines are designed for different purposes, and the amount of gas to oil needed will vary from engine to engine. Common ratios for Lawn-Boy lawnmowers are 16:1, which uses 8 oz. of two-cycle engine oil per gallon of gasoline; 32:1, which uses 4 oz. of two-cycle engine oil; and 50:1, which uses 2.6 oz. of two-cycle engine oil.
The main components in gasoline begin breaking down in as little as 30 days, rendering the gasoline useless. Hard starts, erratic idling and poor acceleration are all signs of bad gas. Only mix the fuel that can be used in 30 days or less. If you need to keep fuel for longer periods, add a stabilizer the day the fuel gets mixed. When fuel stabilizer is added to the fuel, it can keep for four to six months. Dump out any old or bad gas immediately, as using it may damage the carburetor and engine.