The Simplicity Coronet mower engine is under the operator's seat. To access the drain tube and fill tube requires lifting the seat off the mower. Simplicity recommends changing the oil every 25 hours or the beginning of each mowing season. They also recommend using SAE 30 motor oil when changing the oil. The mower comes with a hose to attach to the end of the drain tube. If you are unable to locate the original hose, a replacement piece of hose is available at auto parts stores.
Park the Simplicity Coronet mower over a level surface, and set the brake. Take the ignition key out of the ignition. Grab the back of the seat, and lift it forward. The seat will rest in the forward position.
Locate the oil drain tube near the base of the oil fill tube toward the rear of the engine. Attach a 1/2 inch diameter hose to the end of the drain tube until the hose seats close to the valve nut. Direct the other end of the hose over the container to catch the oil.
Turn the valve nut counterclockwise with a crescent wrench to open the drain valve. When oil stops flowing out of the drain tube, turn the valve nut clockwise to close the drain tube. Pull the hose off the end of the drain tube, and wipe the end of the drain tube with a rag.
Unscrew the oil fill cap, and pull out the oil dipstick. Add two pints of SAE 30 motor oil. Wipe the dipstick with a clean rag. Insert the dipstick into the fill tube, and turn the cap clockwise to seat the dipstick. Turn the cap counterclockwise and remove the dipstick to check the oil level. Add oil as necessary until the oil level is at the full mark on the dipstick. Add oil in half pint increments to prevent over filling.
Place the dipstick into the fill tub, and screw the cap onto the tube. Lower the seat back into the operating position.