Properly maintaining lawn equipment including push mowers saves money by increasing the lifespan of the equipment. For gasoline engines, maintenance involves changing the oil on a regular basis. For push mowers, change the oil every 50 hours of operation or once every season. Not all push mowers are designed the same, but most do not have a drain plug on the bottom of the mower that can be pulled to allow the old oil to drain.
Start the lawnmower and allow to run normally for one minute to warm the oil. Turn the engine off and disconnect the spark plug. Position a screwdriver longways into the middle of the "U" at the top of the push lawnmower drain plug where the oil is normally checked and added. Turn counterclockwise to unscrew the plug.
Place a drain pan on the side of the lawnmower so oil can drain from the drain plug hole into the pan after the mower is tilted on to its side.
Tilt the lawnmower on its side by using the handle as leverage or lifting the mower on the opposite side of the drain plug.
Allow the warm oil to drain from the tilted lawnmower into the drain pan. Use caution in case the oil is hot. Not all the oil will drain out; about one fourth of the oil will remain in the lawnmower.
Replace oil until full or until the dipstick (if the lawnmower has one) shows full with the type of oil required by the owners manual. Most push mowers use standard SAE 30W oil. Replace cap over the oil plug and tighten the cap until firm. Do not overtighten the drain plug or you may strip out the thread on the cap.