Insert a siphon into your gas tank. Place the other end in a gasoline can. Press the siphon bulb to remove the gas from the tank.
Pull on the spark plug cord to remove it.
Loosen the screw on the air filter cover and pull the air filter cover off. Pull out on the filter and press in a new one.
Turn the mower onto its side with the oil crankcase sitting underneath the carburetor.
Hold on to the mower blade with a gloved hand and turn the bolt in the center of the blade with a ratchet. Pull the blade off the unit.
Set a drain pan underneath the mower and unscrew the oil plug with a wrench. Allow the oil to drain into the pan. Replace the plug once the oil has drained from the unit.
Scrape all the dirt from the underside of the mower using a putty knife. Replace the mower blade.
Remove the spark plug using a ratchet and replace it if it appears rusted or cracked.
Fill the oil crankcase with lawnmower oil.
Fill the gas tank with unleaded gas.