The lawnmower must endure not only severe temperature extremes, but perhaps hostile abuse by its operator. The small engine that turns the lawnmower blade must be kept in tiptop condition to perform efficiently. Regular maintenance can greatly extend the life of the lawnmower. One of the best maintenance acts that can be done to the small machine is changing the engine oil on a regular basis. Most manufacturers, depending on model and type, recommend that the oil be changed every 25 to 50 hours of operation.
Set the lawnmower on a firm and level surface. A concrete slab or asphalt driveway is preferable so any spills can be readily cleaned.
Remove the spark plug wire from the top of the spark plug. The thick rubber hood connection is generally located at the rear of the small engine that faces the push handles.
Siphon all gasoline from the fuel tank. Insert the long end of the hand siphon pump into the lawnmower fuel tank. Place the short hose into the gasoline container. Press the rubber bulb several times to drain the fuel tank.
Locate the oil drain plug on the lawnmower. It will be a square-necked plug on the lower portion of the engine. Typically it is positioned near the side of the engine, just below the oil filling orifice. In some lawnmowers, it may be located under the lawnmower cutting deck. If so, tip the lawnmower on its side. Keep the fuel tank and carburetor to the upper side when tipping the mower.
Loosen the oil drain plug by fitting the crescent wrench over the square neck of the plug. Turn the wrench counterclockwise. Remove the plug with your fingers. Allow the oil to drain into the oil collection container.
Replace the oil drain plug once all the oil has drained from the engine. Tighten the plug with the crescent wrench. Clean up any spills with the rags. Set the lawnmower back to a level position, if applicable.
Open the oil filling orifice. Place the small funnel inside. Fill the engine with the correct type of oil specified by the engine manufacturer. Consult the engine specifications for the total amount of oil required. Different engines will have different oil fill requirements.
Replace the oil filling cap. Fill the fuel tank with fresh gasoline. Insert the rubber hood spark plug wire back over the top of the spark plug.