How to Change the Oil in a Lawn Mower

Last Updated: May 6, 2021

Lawn mowers, like cars, need their oil changed every now and then. Not changing the oil in a lawn mover can significantly reduce its lifespan. If you are wondering how to change the oil in your lawn mover, then you came to the right place. This wikiHow will tell you how you can change the oil in a lawn mover.

Steps

1
Unplug the spark plug wire before any repair or maintenance is made to any mower.^{[1]
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2
Use a hand siphon hose from auto or hardware store to empty gas from the tank.^{[2]
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Research source}This prevents spillage onto mower deck & prevent possible fire if ignited by spark plug later. A damaged spark plug wire or plug may ignite any gas spilled.
3
Look under the mower deck for the oil drain plug.Most are square & recessed for a socket wrench set,socket extension fit (3/8's) drive.Others may be just a common drain plug or bolt^{[3]
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4
Either prop the mower or hold up & use the socket to loosen the drain plug or bolt.Be sure to have a drain pan under the deck to catch the used oil.
5
After oil is a mere drip re-install the drain plug or bolt, but do not over tighten or strip.Drain the used oil into an empty oil container (or suitable container) using a funnel, for future "safe" disposal at a local Hazardous Waste Disposal Site.These sites are usually managed by local landfill sites.^{[4]
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6
After drain plug is closed & has a proper seal,prepare to then refill the oil filler hole to proper fill point.Some mowers have the filler hole on top with a dip stick while others are lower on engine near the deck.This type does not have a dip stick, but must be filled to limit,near cap space.Use standard S.A.E 10w30 or 5w30 motor oil.^{[5]
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7
Check to see that oil cap is installed on filler & then refill gas tank & attach spark plug wire.

Community Q&A

Question

Petrol was mistakenly put in the oil tank. What should I do?

Community Answer

First, drain the tank of the petrol using the same technique used on the oil. Then, leave the tank open in a place where air can flow through the tank in order that the remaining petrol evaporates, making sure that no debris makes its way into the tank. Using a fan and waiting 24 hours would be the safest option, and be sure not to let any dirt or bugs get into the tank in the meantime.
Question

Can I just tilt my lawn mower to drain oil?

Community Answer

Yes, but remove the gas cap first, and put some plastic wrap over it. Put the gas cap back on, then go ahead and turn your mower on its side to drain oil. The plastic wrap keeps the gas from leaking out. Once the oil change is done, remove the plastic wrap from the gas cap.
Question

Why do you need to remove the spark plug to drain the oil?

Community Answer

You should detach the plug wire to prevent any chance of the engine starting. It would be dangerous if you somehow spun the blade while working underneath and the run stop switch was engaged.
Question

When is new oil too old to be used?

Community Answer

As long as it's sealed, it should be fine. If it has been opened and especially if it has been sitting out for a long time, moisture may build up, but as long as the cap is still on, it should be good for a few years.
Question

Why is my lawnmower smoking?

Community Answer

Not unlike a car, if oil has been used beyond it's engine protection limit, it loses viscosity. Another reason could be your engine needs serviced.
Question

Can I use synthetic motor oil from a parts store or do I need to stick with the 4-cycle oil from a lawn and garden store?

Community Answer

Check the owner's manual (you can probably find it online if you don't still have yours). If still under warranty, it's best to go by the manufacturer's recommendations. If it's an older mower, you can simply use 10W30 or 5W30. If in doubt, though, stick with 4 cycle engine oil or another suitable substitute.
Question

Should I do anything special before draining the oil if it hasn't been changed in a long time?

Community Answer

No. You can flush with engine oil itself until you see clear oil come through the drain plug.
Question

Should I check the oil when it is hot or cold?

Community Answer

Always check when your engine is cold, as engine oil will stay coated in motor when hot or still warm. Oil should be at the full mark of the dip stick or the top of the filler reservoir.
Question

How much oil do I put in a normal lawn mower?

Community Answer

Fill it only to the "full" mark shown on the oil dipstick or reservoir.
Question

If I put coolant where the motor oil should be, do I need to replace my lawn mower?

Community Answer

Do not start your mower. Drain the motor oil/coolant mix, and flush the remaining coolant out by pouring motor oil through until only clean oil is left flowing out of the mower. Place the drain plug back, and fill the mower with oil normally, and you should have no issues.

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Warnings

Use caution when handling used oil. You may wear rubber or latex gloves.

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Before oil change remove spark plug wire from plug & drain fuel to prevent spills or possible spark from plug later when started up.

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Dispose of used oil "safely" at any Hazardous Waste Disposal Site that accepts it.

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