Mower care: change the fuel filter, oil, and spark plugs

June 19, 2015

Manufacturers all recommend different "service intervals" for things like oil, filter and spark plug changes. Some recommend greasing moving parts every 50 hours, and others call for it every 25 hours. Best to check your manual.

Mower care: change the fuel filter, oil, and spark plugs

Every manufacturer recommends different "service intervals" for things like oil, filter and spark plug changes. These intervals can vary a lot. Many manufacturers recommend greasing moving parts every 50 hours, but some call for it every 25 hours. So don't follow general guidelines — follow your manual.

Replacing the oil filter

  • An old fuel filter can cause hard starting, poor fuel economy, maybe even an expensive carburetor rebuild. Check your owner's manual to find out how often to replace the filter.
  • Replacing the fuel filter is easy. But there's a trick to doing it without getting drenched in gasoline.
  • First, pinch the fuel line leading from the tank with a clamp.
  • Then move the spring clamps away from the filter with pliers.
  • Slip on a pair of nitrile gloves, tilt the inlet side of the filter up and remove the inlet hose.
  • Drain the small amount of fuel from the fuel line into a drain pan.
  • Then, plug the filter inlet with your thumb, tilt the entire filter down, and pull it out of the outlet hose.
  • This technique keeps most of the fuel inside the filter, reducing spillage.
  • Place the old fuel filter in the drain pan and install the new filter.
  • Pay attention to the fuel flow direction arrows — the arrow must point toward the engine.
  • Move the fuel line clamps back into place and remove the "pinch-off" clamp from the fuel line.


Get a smaller gas can. Old gas (stored for more than 30 days) is the most common cause of starting problems.

Choose the right oil

Just like your car, your tractor needs regular oil changes. If your owner's manual suggests a brand of oil, you can ignore that advice. But do pay attention to the recommended viscosity (such as 10W-30).

If you use your tractor for snow removal, check the manual for a "winter weight" oil recommendation. Never, ever change the oil without also changing the oil filter. To prevent a buildup of gunk on the engine, wipe up any spilled oil. Bottle the old oil and take it to your nearest oil recycling centre for disposal.

Spark plug pointers

Worn spark plugs cause a variety of problems, from hard starting and poor fuel economy to misfires and even engine damage. So replace them at the manufacturer's recommended intervals. Changing plugs is a simple matter of unscrewing the old ones and screwing in new ones. But there are a few things to keep in mind:

  • Prevent debris from falling into the cylinder by brushing or blowing around the plug before you remove it. After removing the plug, wipe out the spark plug seat with a clean rag.
  • If an old plug won't turn, don't resort to a bigger wrench. Brute force can cause major engine damage. Instead, use a spray that instantly cools the plug, causing the metal to contract and loosen. The spray is available at most auto parts stores or online.
  • Don't forget to set the gap of the new plugs before installing them. Check the manual for gap specifications and use a gap gauge.
  • Use just the right amount of force to tighten the plugs. If you don't have a torque wrench, follow this general rule: First, finger-tighten the plug. If the plug has a gasket, tighten it an additional half turn using a plug wrench. If the plug has a tapered seat, tighten it an additional one-sixteenth turn.
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