Lawn mower oil: what type, and how it is changed

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Your mower's manual says which oil it takes, how much, and when to change it. We give no oil grade and no amount, because those come from the maker and engines differ. This guide covers which mowers take engine oil, what extension services say about checking and changing it, and what EPA says to do with used oil. It links back to our maintenance basics guide.

Why does the oil matter?

EPA says oil keeps machines such as lawnmowers "running smoothly." It says that in normal use, dirt, metal scrapings, water, or chemicals get into the oil, and that in time it no longer does its job. UGA says that when small engines are properly kept up, both two-cycle and four-cycle types are "quite reliable."

Which mowers take engine oil?

UGA says four-cycle engines, the kind found on lawnmowers and garden tractors, have one reservoir for gas and a separate one for engine oil. It says two-stroke motors "require a mixture of fuel and special two-cycle oil" and "do not have a separate reservoir for motor oil." A two-stroke engine takes its oil in the fuel, at the ratio its manual gives.

A battery or corded electric mower has no engine oil.

What type of oil does a lawn mower use?

The one its manual lists. UGA says to "reference your owner's manual for the oil capacity and type." LSU AgCenter says to add "the recommended amount of the recommended quality and viscosity of oil". Neither one names a grade for every engine, and neither do we. The same rule applies to a riding mower: its manual sets the oil.

When should the oil level be checked?

UGA says to check that the engine oil is at the proper level each day, or each time the equipment is used. The CPSC says to check the manual for hints on routine maintenance, including engine oil levels. Ohio State lists keeping proper oil levels among its maintenance points.

When should the oil be changed?

The manual sets the schedule. UGA says "Engine oil should be changed once a year in your garden equipment." LSU says "The first thing you should do to prepare any 4-stroke engine for storage is to change the oil and oil filter." Where the manual gives a different schedule, follow the manual.

How is the oil changed?

We give no steps; the manual sets them for your mower. LSU describes the job in its storage checklist. It says to drain the old oil, and that "If you do this when the engine is warm, the oil will flow better" and carry more dirt out with it. It says to replace the oil filter if the machine has one, add oil in "the recommended amount" and type, and then check the level to be sure.

Before any of it, Ohio State says to "shut off the engine and disconnect the spark plug wire before performing maintenance". LSU does not say how warm. The manual says when and how the oil on your engine is drained.

What do you do with the used oil?

EPA says used oil from a lawnmower, a car, or a bike can harm soil and water when it is not recycled or disposed of the right way. It says that "Recycling used oil keeps it from polluting soil and water." It says to avoid spills when collecting used oil and to keep it in a "leak-proof can or container." It says to ask local auto service shops, waste haulers, and local government waste offices where to drop it off, and it says used oil filters can be drained and recycled too.

Sources: University of Georgia Extension, Equipment Maintenance and Troubleshooting for the Landscape and Garden (Circular 1247); LSU AgCenter, Preparing Small Engines for Storage; Ohio State University Extension, Power Lawn Mowers; CPSC, Power Lawn Mowers (Publication 5126, PDF); EPA, Managing, Reusing, and Recycling Used Oil.

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