Turn off your John Deere 314 lawn mower and open the front hood that conceals the engine.
Check the right side of the engine for the spark plug, where the black ignition wire connects. Pull the ignition wire out of the rear of the spark plug before proceeding, for your safety.
Find the oil drain plug on the bottom rear of the mower, near the wheels. Place a pan under the drain plug and unscrew it to release all the old oil into the pan. Set the drain plug back into place.
Remove the cap and dipstick from the oil reservoir. Fill the tank with SAE 30-quality motor oil. Check the oil level using the dipstick and ensure the level of oil within the oil reservoir goes up to the "FULL" line on the dipstick, but no higher.
Put the oil reservoir's dipstick and cap back into place.
Insert the ignition wire into the rear of the spark plug once more. Close the engine's hood.