Oil Mixture to Old Lawn-Boy Mowers

Mixing the right oil-to-gasoline ratio in a two-cycle engine lubricates internal components, preventing damage to the motor. If you own a Lawn-Boy mower equipped with a D-400 string engine, fabricated from the late 1970s through 1983, Lawn-Boy recommends a 16:1 ratio of gasoline to oil to keep the engine properly lubricated. Since the oil-to-fuel ratio can vary dependent on the year the device was fabricated, prevent under- or even overmixing by checking the owner’s manual for the appropriate ratio. Also, keep in mind gasoline is flammable. Prevent a fire by turning off the mower’s engine before mixing fuel, rather than mixture gasoline near an open fire.

Utilize Right Octane Rating

Ensuring that your mower runs its best means using the correct grade of gasoline along with two-cycle oil. Lawn-Boy recommends using unleaded gasoline using an octane rating of 86 in its D-400 string engines. The manufacturer warns against using gasoline containing ethanol or methanol, and not to use automotive grade oil. To prevent hard-starting motors, always use fresh gasoline — gas maybe not over 30 days old. Stale gas can cause gumming in the gas line.

Mixing Ratio

If you have lost the manual for your mower’s engine, another area you can find the right oil-to-gas mixing ratio is about the motor’s housing — the outer part of the engine. Look for a small plate with the mixing ratio stamped on it, or it might be stamped directly onto the engine. If you do not locate the ratio on the motor, Lawn-Boy recommends combining 8 ounces of any non-Lawn-Boy brand two-cycle motor to 1 gallon of gasoline for its D-400 string engines manufactured from the late 1970s through 1983. Make sure the oil is a high-quality two-cycle oil. For a smaller batch, mix 4 ounces of two-cycle oil to 1/2 gallon of gasoline.

How to Mix

To ensure the motor is properly lubricated, the petroleum and gasoline has to be thoroughly mixed before pouring it in the gas tank. Not fully mixing the oil and gas could cause inadequate lubrication and motor damage. To correctly mix fuel, measure the recommended amount of two-cycle oil to your plastic Department of Transportation-approved gas container, then add the recommended amount of gasoline. Replace the container’s cap, then gently swirl the gas and oil together. Do not vigorously shake the container.

Indications of Wrong Oil Ratio

If you haven’t combined the suitable number of two-cycle oil to the gasoline, your motor will let you know. Not enough oil causes scoring, or grooves, on the pistons, and when not corrected eventually, the motor seizes and is not repairable. Adding too much oil causes blue smoke to billow from the exhaust along with oil splatters. An excessive amount of oil is not as harmful as not enough, but if you see signs of it, then drain the gas tank to your DOT-approved container and remix the oil and gas to the right ratio.

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