After you assemble your new lawn mower, it is important to break in its mower engine. This breaking-in process will remove any loose debris from the motor housing and also heat up the engine seals. The warming and subsequent cooling of the seals and the lubrication from the oil will help the seals remain pliable and function properly. By running the engine and then performing an oil change, you will also remove any loose metal shavings that may be inside the engine.
Things You'll Need
SAE 30 motor oil
Remove the oil fill cap, then fill the mower with oil to the specifications in your owner's manual. Most manufacturers include a bottle of oil in the shipping box. The standard oil in many lawn mowers should be SAE 30 detergent motor oil.
Use the dipstick connected to the oil cap to check the oil level. Secure the oil fill cap to the mower when the oil level is correct.
Fill the fuel tank with a quarter tank of gas. By filling the tank only a quarter full, you will avoid fuel spillage when it is time to change the oil.
Place the mower throttle in the start position and press the primer bulb on the side of the engine three times until you see fuel in the bulb. Pull the starter cord and start the mower engine.
Allow the mower engine to idle for five minutes, then raise the throttle to the "run" position. Allow the engine to stay in that position for five minutes.
Lower the throttle to idle for five more minutes and shut the lawn mower engine off. Allow the engine to cool for twenty minutes.
Place an oil catch container next to the mower's oil fill side. Remove the oil fill cap and tilt the mower to drain the oil from the fill cap into the container. Lower the mower back on all four wheels after the oil has drained.
Wipe the mower down with a clean shop rag to remove any oil spillage on the deck or around the fill hole, then pour the appropriate amount of SAE 30 oil into the oil fill hole. Check the oil level with the dipstick until the oil is at the correct level. Place the dipstick and oil fill cap back on the engine.