A large part of lawn mower maintenance is changing the oil. A lawn mower's engine oil should be changed after the first 5 operating hours and then every 50 hours of operation or every season. In dusty or dirty conditions, oil changes may need to be more frequent.

If operating under heavy loads, extreme use, or high temperatures, engine oil should be changed every 25 operating hours.

As per owner's manual

  1. Run the engine for a few minutes to warm the oil. Warm oil flows better and will carry more contaminates.
  2. Stop engine and wait for moving parts to stop.
  3. Disconnect the spark plug wire.
  4. Remove drain plug and drain oil. Some mowers don't have plugs and need to be tipped over to drain oil out of the dipstick/filling port. Refer to owner's manual to avoid spilling gas or contaminating air filter.
  5. Install drain plug or return mower to operating position.
  6. Fill the crankcase to the "Full" line on the dipstick. Use oil recommended by the owner's manual and add a little at a time until full.
  7. Install dipstick
  8. Use a rag to wipe up any spilled oil.
  9. Recycle used oil according to local ordinances. Do not dump used oil down the drain!

 Spark Plug

Part of a complete lawn mower maintenance program is servicing the spark plug. An old spark plug may be dirty, pitted, covered in carbon, or have worn electrodes, resulting in hard starting and poor operation.

The spark plug should be cleaned or replaced after 50 operating hours. The type of spark plug for your mower will be listed in the owner's manual.

  1. Stop engine and wait for moving parts to stop.
  2. Disconnect spark plug wire.
  3. Clean debris around the spark plug housing.
  4. Remove the spark plug with appropriate deep socket and clean it with a wire brush, removing any carbon buildup.
  5. Inspect the plug for cracks, damage, or worn electrodes. Replace if necessary.
  6. Set the gap on the plug to manufacturer's specs. See owner's manual.
  7. Install the spark plug by hand, then gently tighten it with the socket wrench. Do not over-tighten and break spark plug
  8. Reconnect the spark plug wire.

Quick Tip to Avoid Engine Smoke and Dirty Air Filter

When turning a mower on its side either for cleaning, maintenance, or inspecting the blade, it's important to try to direct the exhaust system upward. Doing this will help prevent oil from running up into the carburetor, where it will burn and smoke. Eventually it will make its way to the air filter and getting it filthy, resulting in decreased engine performance.