Lawn mowers in the Craftsman brand DYT4000 series, which feature different engine models, horsepower levels and cutting path widths, require regular oil changes to keep the engine running smoothly. Craftsman recommends checking the oil before each use and after every eight operating hours. Oil should be changed after every 50 hours of operation or once a year if you use the mower less than 50 hours a year. Use high-quality engine oil that meets the API service classifications SG through SL with the viscosity recommended for your particular DYT4000 model.
Move the mower to a level surface and engage the parking brake. Lift the hood and disconnect the spark plug wire, located at the front of the engine, using your fingers to gently lift it away from the spark plug. Keep the wire clear of the spark plug while you are changing the oil.
Wipe the area around the oil filler cap to clean off any dirt, grass and debris before removing the oil filler cap to avoid getting dirt in the engine. Unscrew the oil filler cap, wipe off the dipstick and place it in a clean bag or wrap it in a clean towel while you change the oil.
Remove the yellow cap from the end of the oil drain valve and insert the oil drain tube on the valve fitting. Place the other end of the drain tube in the bucket before you open the drain valve.
Push in and turn the drain valve counterclockwise to unlock it, and then pull it out to let the oil drain into the bucket.
Let all the oil drain from the mower, and then push the drain valve in and turn it clockwise until it locks. Remove the oil drain tube and push the yellow cap back on the end of the drain valve.
Insert the funnel into the oil fill tube and slowly pour new oil into the engine.
Replace the oil fill cap and tighten it completely. Remove the cap and look at the dipstick to check the oil level. Craftsman recommends keeping the oil at the dipstick's “Full” line for best performance. If the level is low, add more oil a little bit at a time, check the level again and repeat until it reads full. Replace and tighten the oil fill cap when you finish.
Wipe off any spilled oil near the oil fill tube and by the oil drain valve. Replace the spark plug wire by pushing it back onto the spark plug.