Changing lawn mower oil takes 15 to 30 minutes and requires only basic tools you likely have at home

Lawn mower oil gets dirty and breaks down over time, which means your engine works harder and wears out faster. Changing the oil yourself costs a few dollars for new oil and a filter, versus $50 to $100 at a repair shop. The process is straightforward: drain the old oil, replace the filter if your mower has one, add new oil, and check the level. Most homeowners can do this without special skills or equipment.

The exact steps depend on whether your mower is a push mower, riding mower, or zero-turn model, but the principle is the same for all of them. This guide covers the most common setup: a small engine with a drain plug underneath and an oil filter on the side or top.

Key Takeaways

  • Drain old oil while the engine is still warm but cool enough to touch safely, because warm oil flows faster and leaves less sludge behind.
  • You will need new oil in the weight your mower's manual specifies (usually SAE 30 or 10W-30), a wrench or socket to remove the drain plug, and an oil filter wrench if your mower has a filter.
  • The oil filter, if present, should be replaced every other oil change or once per season, whichever comes first.
  • Overfilling the oil damages the engine just as much as running low, so check the level with the dipstick after adding new oil and stop when you reach the full mark.

Gather your materials before you start

You will need the correct oil type and weight. Open your mower's manual or look for a sticker on the engine itself — it will say something like "SAE 30" or "10W-30". Buy a quart or two of that exact type. Most small mower engines use SAE 30 in warm months and 10W-30 in cold months, but your manual is the authority.

Collect a wrench or socket set (usually 12mm, 14mm, or 17mm for the drain plug), a drain pan large enough to hold at least a quart of oil, and rags or paper towels. If your mower has an oil filter — check by looking at the engine block for a cylindrical canister about the size of a soda can — you will also need an oil filter wrench, which costs $5 to $10 at any hardware store and grips the filter so you can unscrew it by hand.

Set up in a flat, level spot outdoors or in a garage with good ventilation. Oil spills are messy and can damage concrete, so lay down cardboard or newspaper under the mower.

Warm the engine and locate the drain plug

Run the mower for two or three minutes to warm the oil. Warm oil flows faster and drains more completely, leaving less sludge in the engine. Let it cool for five minutes — the engine should be warm to the touch but not so hot you cannot hold your hand near it. This balance matters: oil that is too cold drains slowly, and oil that is too hot can burn you.

Tip the mower on its side to access the drain plug underneath. Check your manual first to see which direction is safe — on some models, tipping one way can flood the carburetor with oil. If you are unsure, tip it toward the side where the air filter is located. The drain plug is a bolt sticking out from the lowest point of the engine block, usually with a hex head you can grip with a wrench.

Place your drain pan directly under the plug. Unscrew the plug slowly with your wrench — oil will start flowing when ready. Once the plug is loose enough, unscrew it by hand and set it aside on a rag. Let the oil drain for five to ten minutes. If very little oil comes out, the engine may have been run recently and the oil is still hot, or the mower may be low on oil already.

Replace the oil filter if your mower has one

Not all lawn mowers have an oil filter. If yours does, it will be a cylindrical canister screwed onto the side or top of the engine block. Locate it now, before you refill with new oil. If there is no filter, skip this section.

Position your drain pan underneath the filter — old oil will spill when you remove it. Grip the filter with your oil filter wrench and turn it counterclockwise to unscrew it. Once it is loose, unscrew it by hand and set it aside. Wipe the filter mounting surface clean with a rag to remove any old rubber or debris.

Take your new filter and coat the rubber gasket (the flat ring around the top) lightly with new oil. Screw the new filter on by hand until the gasket touches the mounting surface, then turn it another three-quarter turn. Do not use the wrench to tighten it — hand-tight is correct. Over-tightening damages the gasket and makes the filter hard to remove next time.

Install the drain plug and add new oil

Wipe the drain plug clean and screw it back into the hole by hand first, then tighten it with your wrench. It should be snug but not cranked down hard — you are sealing a hole, not anchoring a bolt. Over-tightening can strip the threads and cause a leak.

Stand the mower upright on level ground. Locate the oil filler cap on top of the engine — it usually has an oil can symbol on it. Unscrew it and set it aside. Insert a funnel into the opening and pour in new oil slowly. Most small mower engines hold between 0.5 and 1.5 quarts, but your manual will say exactly how much.

Add oil gradually and check the level with the dipstick as you go. The dipstick is usually attached to the underside of the filler cap. Wipe it clean, reinsert it fully, then pull it out again to read the level. The oil should reach the full mark — not above it. Overfilled oil foams inside the engine and reduces lubrication, which causes damage just as serious as running low.

Check your work and run the engine

Screw the filler cap back on and wipe up any spilled oil with a rag. Start the engine and let it run for 30 seconds to a minute. This circulates the new oil through the engine and helps the new filter fill with oil. The oil pressure light (if your mower has one) should come on briefly when you start, then turn off once the engine is running — this is normal.

Stop the engine and wait five minutes for the oil to settle. Check the dipstick one more time to confirm the level is still at the full mark. If it is low, add a small amount more and recheck. If it is high, you overfilled — use a turkey baster or syringe to remove a small amount of oil until the level is correct.

Dispose of the old oil properly. Many auto parts stores and recycling centers accept used oil for free. Do not pour it down a drain or into the ground — it contaminates water supplies and is illegal in most places.

How often to change your mower's oil

Change the oil every 50 hours of mowing, or once per season if you mow less than that. If you mow frequently during summer, that might mean every four to six weeks. If you mow a small yard once a week, once per season is enough. Check your manual for the manufacturer's recommendation — some engines are designed for longer intervals.

Replace the oil filter every other oil change, or once per season if you change oil only once a year. A clogged filter restricts oil flow and defeats the purpose of changing oil in the first place. If you mow in dusty conditions, check the filter more often and replace it sooner.

Keep a log of when you changed the oil and how many hours the mower ran. This helps you stay on schedule and shows a potential buyer that the mower was maintained if you ever sell it.

Frequently Asked Questions

What if I cannot find the drain plug?

Check your mower's manual first — some models have the drain plug in an unusual spot. If you still cannot locate it, look at the lowest point of the engine block when the mower is level. The plug is always at the bottom so gravity can drain the oil. On some older or smaller mowers, there is no drain plug at all; instead, you tip the mower and pour the oil out directly through the filler opening.

Can I use the same oil weight year-round?

Check your manual. Many mowers use SAE 30 in warm months and 10W-30 in cold months because thicker oil flows poorly in winter and thin oil does not protect the engine in summer heat. Some newer engines are designed to run 10W-30 all year. Using the wrong weight reduces engine life and may void your warranty.

What if oil leaks from the drain plug after I reinstall it?

The plug may be stripped or the gasket may be damaged. Remove the plug, inspect the threads, and try reinstalling it. If it still leaks, the threads are likely stripped and the plug needs to be replaced — they cost $2 to $5. Do not overtighten a new plug; hand-tight plus a quarter turn with the wrench is correct.

Do I need to change the air filter when I change the oil?

No, but check it while you are working on the mower. The air filter is usually a foam or paper element near the top of the engine. If it is visibly dirty or clogged, replace it. A dirty air filter makes the engine work harder and use more fuel, but it does not require an oil change schedule.

Can I recycle the old oil filter?

Some recycling centers accept oil filters, but many do not because they still contain oil. Call your local recycling program or auto parts store to ask. If they will not take it, drain as much oil as possible from the filter into your drain pan, then throw it in the trash.