Change lawn mower oil

Change your lawn mower oil for reliable engine performance all season.

Why it matters#

Clean oil protects engine components and ensures reliable operation. Old oil breaks down and can cause costly engine damage.

What you'll need#

Tools#

Socket wrench or drain plug tool
Drain pan or container
Funnel
Clean rags

Materials#

New oil (SAE 30 or 10W-30, check manual—typically 18-20 oz)

Steps#

1. Run the engine briefly#

Start the mower and let it run for 2-3 minutes. Warm oil drains more completely.

2. Turn off and disconnect spark plug#

Stop the engine and disconnect the spark plug wire to prevent accidental starting.

3. Position the drain pan#

Place your drain container where the oil will exit—under the drain plug or under the fill tube depending on your method.

4. Drain the oil#

If your mower has a drain plug: remove the plug and let oil drain completely. If no drain plug: run the fuel low first, then tip the mower with the air filter side UP and drain through the fill tube.

5. Replace the drain plug#

Once oil stops flowing, replace and tighten the drain plug (if applicable). Don't overtighten.

6. Add new oil#

Set the mower level. Using a funnel, add new oil slowly. Most walk-behind mowers take 18-20 oz, but check your manual.

7. Check the level#

Use the dipstick to check the level. Add oil in small amounts until it reads at or just below the full mark. Don't overfill.

9. Run and recheck#

Start the engine and let it run for a minute. Turn off and recheck the oil level—top off if needed.

10. Dispose of old oil properly#

Take used oil to an auto parts store or recycling center. Never pour it down drains or in the trash.

Pro tips#

Change oil at the start of each mowing season and every 50 hours of use
Always tip the mower with the air filter UP—tipping the other way floods the air filter with oil
Write the date on a piece of tape on the mower so you know when oil was last changed
If oil looks milky, water has gotten in—change it immediately

Warnings#

Always disconnect the spark plug before working on the mower
Hot oil can burn—let the mower cool slightly after the warm-up run
Never overfill—too much oil causes smoking and can damage the engine

Oil changes don't typically require professional service. However, if you notice metal particles in the oil or the engine is burning through oil quickly, the engine may have internal problems worth having a small engine repair shop evaluate.