The basic steps: drain, replace the filter, add new oil

Changing your lawn mower's oil takes about 15 to 20 minutes and requires only a few tools you likely have at home. The process is: run the engine briefly to warm the oil, turn it off and let it cool for a few minutes, drain the old oil into a container, replace the oil filter if your mower has one, and pour in the correct amount of new oil. Most mowers need an oil change every 50 to 100 hours of use, or at least once a year if you use it less often.

The reason you change oil is that it breaks down over time and loses its ability to protect the engine from wear. Fresh oil keeps metal parts from grinding against each other and helps the engine run cooler. Skipping oil changes shortens your mower's life and can leave you stranded mid-season.

Key Takeaways

  • Warm the engine for a minute or two before draining so the oil flows out completely, then let it cool just enough that you can touch the mower without burning yourself.
  • Find the drain plug underneath or on the side of the engine, unscrew it by hand or with a wrench, and let the old oil drain into a shallow pan for at least five minutes.
  • If your mower has an oil filter (usually a small cylinder on the engine), unscrew it by hand, wipe the rubber gasket area clean, and screw on a new filter until the rubber seal just touches, then turn it three-quarters of a turn more.
  • Check your mower's manual for the exact oil type and amount — most small mowers use SAE 30 or 10W-30, and most hold between 0.5 and 2 quarts.
  • Pour oil slowly through the filler cap, check the level with the dipstick after each addition, and stop when the oil reaches the full mark.

What you need before you start

Gather these items before you begin: a shallow pan or old container to catch the used oil (a cake pan or old oil bottle works), a wrench or socket set if your drain plug is tight, a new oil filter if your mower has one, the correct type and amount of new oil, and a clean rag or paper towels. You will also need your mower's manual or the information printed on the engine itself, which tells you what oil weight to buy.

Used oil cannot go in the trash or down the drain. Most auto parts stores and many gas stations take used oil for free, even if you did not buy oil from them. Some municipalities have hazardous waste collection days. Call ahead to confirm they accept small quantities from homeowners.

Finding the drain plug and warming the engine

Start by locating the drain plug. On most lawn mowers, it is on the underside of the engine or on one side near the bottom. Check your manual if you cannot find it — the location varies by brand. Some plugs have a small bolt head; others are a straightforward screw you can turn by hand.

Before you drain anything, run the engine for one or two minutes to warm the oil. Warm oil flows out faster and more completely than cold oil. Turn off the engine and wait two or three minutes until the mower is cool enough to touch safely. Do not wait so long that the oil cools completely — you want it warm but not hot.

Draining the old oil

Place your drain pan directly under the plug. If the plug is a bolt, use a wrench to turn it counterclockwise until it comes free, then unscrew it the rest of the way by hand and set it aside where you will not lose it. If it is a screw-type plug, straightforward turn it counterclockwise by hand until oil begins to drip, then unscrew it fully.

Let the oil drain for at least five minutes. Tilt the mower slightly if needed to help the oil flow toward the pan. Once the dripping slows to a few drops per minute, the pan is full enough. Wipe the drain plug clean with a rag, then screw it back in by hand until it is snug. Do not overtighten — you will strip the threads and create a leak.

Replacing the oil filter (if your mower has one)

Not all lawn mowers have an oil filter. Check your manual or look at the engine — if you see a small cylinder (usually two to four inches long) with a nut or cap on top, you have one. If you do not see one, skip this section.

The filter usually sits on the side of the engine. Locate it, place your drain pan underneath, and use an oil filter wrench or a rag for grip to turn it counterclockwise. Once it is loose enough, unscrew it by hand and let any remaining oil drain into the pan. Wipe the rubber gasket area on the engine clean with a rag — this is the flat surface where the old filter was attached.

Take your new filter and explore a thin layer of fresh oil to the rubber gasket (the ring at the base of the filter). This helps create a good seal. Screw the new filter onto the engine by hand until the rubber gasket just touches the engine, then turn it three-quarters of a turn more. Do not use a wrench — hand-tight is correct.

Adding new oil and checking the level

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. Slowly pour in the new oil — start with half the amount your manual recommends, then check the level with the dipstick before adding more. The dipstick is usually attached to the underside of the filler cap or is a separate stick you pull out from the engine.

Wipe the dipstick clean, reinsert it fully, then pull it out again to read the level. The oil should reach the full mark. If it is low, add a little more and check again. Once the level is correct, replace the filler cap and wipe up any spills with a rag.

Run the engine for a minute to circulate the new oil, then turn it off and wait a few minutes. Check the dipstick one more time to confirm the level is still at full — the oil settles slightly after the engine runs. Top off if needed.

Disposing of old oil and keeping records

Pour your used oil into a sealed container — an old oil bottle or milk jug works well. Label it clearly so no one mistakes it for something else. Take it to an auto parts store, gas station, or municipal hazardous waste collection site. Do not pour it down the drain, into the ground, or in the trash.

Write down the date you changed the oil and the number of hours on your mower (if it has an hour meter). This helps you remember when the next change is due. Most mowers need an oil change every 50 to 100 hours of use. If you use your mower weekly during the growing season, that is roughly once a month or once every two months.

Frequently Asked Questions

What if I cannot find the drain plug?

Check your mower's manual first — it will show you exactly where the plug is located. If you do not have the manual, search online for your mower's brand and model number (usually stamped on the engine) plus "drain plug location". If the plug is stuck or rusted, spray it with penetrating oil and wait 15 minutes before trying again.

Can I use the same oil type every year, or does it change?

The oil type depends on your climate and engine design, not the year. Check your manual or the engine itself for the recommended weight — common types are SAE 30 for warm climates and 10W-30 for variable temperatures. Use the same type every time unless your manual says otherwise.

What happens if I overfill the oil?

Too much oil can damage the engine by creating excess pressure and causing seals to leak. If you overfill, remove the filler cap and use a clean rag or paper towel to soak up the excess until the dipstick reads full. Do not run the engine with overfilled oil.

Do I need to change the air filter at the same time?

The air filter and oil filter are separate. Your manual will tell you how often to change the air filter — it is usually every 100 to 200 hours of use. You can change both at the same time if the air filter is due, but they are not connected to each other.

Can I recycle the old oil filter?

Some recycling centers and auto parts stores accept oil filters, but you must drain all the oil from it first. Punch a small hole in the top and let it drain into your used oil container for at least 24 hours before dropping it off. Call ahead to confirm your local facility accepts filters.