Changing lawn mower oil is a 15-minute job you can do yourself with basic tools

Lawn mower oil gets dirty and breaks down over time, just like car oil. Changing it keeps your engine running smoothly and extends the life of your mower. Most mowers need an oil change every 50 hours of use — roughly once a season for a homeowner — though you should check your mower's manual for the exact interval.

The process is simpler than a car oil change because mowers have no oil filter to replace, no drain plug to unscrew, and no undercarriage to crawl under. You tip the mower, drain the old oil into a container, and pour in new oil. The whole job takes about 15 minutes once you have the right supplies on hand.

Key Takeaways

  • You will need new oil (check your manual for the type and amount), an oil drain pan, a wrench or socket to remove the drain plug, and rags or paper towels.
  • Drain the old oil while the engine is still warm but not hot, because warm oil flows faster than cold oil.
  • Tip the mower on its side with the carburetor facing up to prevent oil from leaking into the carburetor during draining.
  • Fill the mower with the exact amount of new oil specified in your manual — overfilling or underfilling both damage the engine.
  • Dispose of old oil at a recycling center, auto parts store, or service station; never pour it down a drain or into the ground.

Gather your supplies before you start

You need four things: new oil, a drain pan, a wrench or socket set, and rags. Check your mower's manual to find out what type and weight of oil it uses — this is usually printed on the engine itself as well. Common types are SAE 30 for warm climates and 10W-30 for cold climates, but some mowers use synthetic blends. Buy the exact type your manual specifies, not a guess.

The drain pan should hold at least as much oil as your mower uses. Most residential mowers hold between 0.5 and 2 quarts, so a small oil drain pan or even a large yogurt container works. You also need a wrench or socket that fits the drain plug on your mower — usually a 10mm, 12mm, or 14mm bolt. If you do not have the right size, bring your mower to a hardware store and try sizes until one fits snugly.

Have rags or paper towels ready to wipe spills and clean the area around the drain plug before you open it. A small funnel makes pouring new oil easier and reduces spills, though it is not required.

Warm the engine and position the mower safely

Start the mower and let it run for two or three minutes, then turn it off. Warm oil flows much faster than cold oil, so the drain takes less time and you get more of the old oil out. Do not let the engine get too hot — you should be able to touch the engine block without burning yourself.

Once the engine has cooled slightly, tip the mower on its side. The carburetor — a small metal box on the side of the engine — must face upward. If you tip it the wrong way, old oil will leak into the carburetor and cause starting problems later. If you are not sure which way is correct, check your manual or look for a label on the mower that shows the safe tipping direction.

Place the drain pan underneath the mower, positioned to catch oil as it flows out. The oil will not come out in a thin stream — it will dribble and splash — so position the pan generously wide.

Remove the drain plug and let the oil drain completely

Locate the drain plug on the bottom of the engine. It is a bolt with a washer underneath, usually on the lowest part of the engine block. Use your wrench or socket to turn it counterclockwise. It will be snug, so explore steady pressure rather than jerking — if it will not budge, explore a penetrating oil like WD-40 and wait 10 minutes, then try again.

Once the bolt is loose enough to turn by hand, unscrew it the rest of the way and set it aside in a clean spot where you will not lose it. Oil will begin dripping when ready. Let it drain for at least five minutes — longer if the oil is still flowing steadily. Tilt the mower slightly if needed to help the last bit of oil drain into the pan.

While the oil drains, wipe the drain plug clean with a rag. Check the washer — a small rubber or metal ring under the bolt head. If it is cracked, flattened, or missing, replace it with a new one before reinstalling the plug. A bad washer causes leaks.

Refill with new oil to the correct level

Once the oil has stopped dripping, wipe the drain plug threads clean and screw the plug back in by hand. Tighten it with your wrench, but do not over-tighten — snug is enough. Over-tightening strips the threads and makes the next oil change harder.

Set the mower upright on level ground. Locate the oil dipstick, which is usually a yellow or orange handle sticking out of the top of the engine. Pull it straight out, wipe it clean with a rag, and push it back in all the way. Pull it out again and look at the oil level. It should be at the "full" mark.

If the dipstick shows low, pour new oil in slowly through the filler opening. Use a funnel if you have one. After pouring a small amount, wait 30 seconds for the oil to settle, then check the level again with the dipstick. Keep adding oil in small amounts until the level reaches the "full" mark. Do not overfill — oil above the "full" line can damage the engine and cause smoking.

Dispose of old oil properly

Old oil cannot go in the trash, down a drain, or into the ground. It is toxic and harms soil and water. Most communities have free disposal options. Call your local waste management department, or search online for "oil recycling near me" to find the closest location.

Many auto parts stores like AutoZone and O'Reilly accept used oil for free, even if you did not buy it from them. Some gas stations and quick-lube shops also take it. Bring the oil in a sealed container — the drain pan works, or pour it into a milk jug or oil bottle with a tight cap. Do not mix old oil with other liquids.

Run the engine and check for leaks

Start the mower and let it run for one minute. This circulates the new oil through the engine and helps you spot leaks. Look underneath and around the drain plug area — you should see no dripping or pooling oil. If oil is leaking from the drain plug, turn off the mower, let it cool, and tighten the plug a quarter turn more. If it still leaks, the washer may be damaged and need replacement.

Turn off the mower and let it sit for two minutes. Check the dipstick one more time to make sure the level is still at the "full" mark. If it has dropped, add a small amount of oil and recheck. Once everything looks good, you are done.

Frequently Asked Questions

Can I change the oil without tipping the mower on its side?

Some mowers have a drain plug on the side that you can access without tipping, but most do not. Tipping is the standard method. Always tip with the carburetor facing up — check your manual if you are unsure which direction that is. Tipping the wrong way lets oil leak into the carburetor and causes hard starting.

What if I spill oil on the ground?

Clean it up when ready with rags or paper towels and dispose of the rags as hazardous waste. If a large amount soaks into soil, contact your local environmental agency for guidance. Small spills on concrete can be cleaned with kitty litter or absorbent material, then swept up and thrown away.

How do I know if my mower uses synthetic or conventional oil?

Check the manual or look for a label on the engine itself. If you cannot find either, call the mower manufacturer with your model number. Synthetic oil costs more but lasts longer between changes. Conventional oil is cheaper. Use whatever your manual specifies — mixing types is fine, but stick to the recommended weight.

What happens if I overfill the oil?

Overfilled oil can leak past the seals, smoke during operation, and damage the engine over time. If you overfill by accident, tip the mower back on its side, place the drain pan underneath, and open the drain plug just enough to let a small amount of oil drip out. Check the level frequently until it reaches the "full" mark.

Do I need to change the oil filter on my lawn mower?

Most residential lawn mowers do not have an oil filter — only an air filter. The air filter keeps dirt out of the engine and should be cleaned or replaced once a season. Check your manual for the location and replacement schedule. If your mower does have an oil filter, your manual will tell you to replace it at the same time you change the oil.