How do you change the oil in yard machines 158cc 21 self-propelled?

To change the oil in a Yard Machines 158cc 21" self-propelled mower, first ensure the engine is cool and the mower is on a flat surface. Remove the oil fill cap and tilt the mower to drain the old oil into a suitable container. Once drained, refill with fresh oil through the fill cap, using the recommended oil type and amount indicated in the owner's manual. Finally, replace the oil cap securely and check the oil level with the dipstick to ensure it's at the proper level.