What Kind of Oil Goes in Lawn Mowers?

Oil. It’s vital in keeping the lawn mower engine components lubricated, but what kind of oil is suitable for a lawn mower? That depends on what kind of mower you use, whether that mower is powered by a four-cycle engine or a two-cycle engine, and even what the outside temperature is.

Manufacturers know best

To take the guesswork out of which oil to use in your lawn mower, you should consult the mower’s user manual or check on-line to see what the mower manufacturer, or mower engine manufacturer, recommends. Still, it’s always valuable to understand the differences between the types of oil available and why that particular type would be recommended for your application.

While automotive engine oil, such as 10W-30 or 10W-40, can be used in a lawn mower engine, it is generally recommended that SAE 30 motor oil be used. SAE 30 motor oil is better suited for the small engines that power lawn mowers, as well as other outdoor power equipment including snowblowers, generators, and pressure washers. It is formulated to efficiently lubricate the engine components in warmer temperatures above 40 degrees Fahrenheit. If you anticipate having to fire up your lawn mower in temperatures below 40 degrees Fahrenheit, it is recommended you use SAE 10W-30 motor oil, although be aware that if the temperature creeps up above 80 degrees Fahrenheit during the cutting season, you’ll need to replace this type of oil more frequently. You can also use SAE 5W-30 in the engine if you anticipate the temperature outside to remain consistently between -20 and 30 degrees Fahrenheit, but, truthfully, this oil is more likely to be used in snowblower engines.

Another option would be to use a synthetic oil, such as 5W30 or 10W30, both of which offer great protection at all temperatures, and improved starting with less oil consumption. Synthetic oil is also more environmentally-friendly, includes a detergent ingredient to help keep engine components clean, and can be changed, or its level checked with a dipstick, just like standard motor oil.

One major factor involving how you use oil to help run a lawn mower engine is the engine itself. You’ll need to know if your mower uses a four-cycle engine or a two-cycle engine.

Four-cycle engines vs. two-cycle engines

While most walk-behind mowers, and all riding mowers, are powered by a four-cycle engine, some compact push mowers rely on a two-cycle engine. The main difference between the two types of engines is that a four-cycle engine requires two revolutions of the crankshaft and piston to draw the fuel and air into the cylinder, ignite it, then exhaust the combustion gases, whereas a two-cycle engine requires just one revolution to do the same thing.

Another crucial difference between the two engine types is how the oil should be added. A four-cycle engine draws gasoline from a fuel tank and has a separate sump to supply the necessary oil. A two-cycle engine requires the gasoline to be mixed with the oil for the engine to operate properly. This can be tricky since attempting to run a two-cycle engine without a suitable oil and gas mix will cause the engine to seize due to insufficient lubrication. If you’re concerned about getting that gas/oil balance right for a two-cycle engine, you can use a pre-mixed fuel and oil product like TRUFUEL 50:1 Mix to fill the tank.

By having a separate sump for oil, a four-cycle lawn mower engine needs to be maintained in a similar fashion to a car engine, meaning the oil should be changed regularly.

How often should I be changing the oil?

How often you change the oil is dependent on how often you use the lawn mower. It’s always a good idea to replace the oil annually, prior to the start of the cutting season. However, if you’re someone who mows your lawn frequently, takes care of various neighbors’ lawns, or runs a lawn maintenance business, it’s recommended that you change the oil on your walk-behind mower after fifty hours of use. If the size of the job requires a riding mower, or a zero-turn mower, then you’ll want to change the oil after one hundred hours of use.

While the procedure for replacing the oil will differ depending on the type of mower you have and the engine model, for most walk-behind mowers, you can usually unthread the oil tank cap, remove the dipstick, if applicable, and carefully tip the mower to empty the old oil into an approved container. Lawnmower engine oil, like car engine oil, can be recycled at most auto parts stores. Once the oil tank is emptied, return the mower to its upright position, and pour the new oil into the oil fill tube. Walk-behind mower engines usually take 15 oz or 18 oz of oil; riding mower engines require 48 oz or 64 oz of oil. To avoid overfilling, pour in approximately three-quarters of the bottle, then check the tank with the dipstick to determine if the oil level is at full. You can then add more oil, as necessary.

Shop for lawn mower engine oil and parts at Repair Clinic

Finding the right oil, along with everything else that will keep your lawn mower engine running smoothly, is easy when you visit Repair Clinic. Whether you’re looking to purchase a tune-up kit to keep the engine humming, or you need to replace an oil filter, carburetor, valve, piston, or primer bulb, Repair Clinic stocks genuine manufacturer parts from the top names in small engines, such as Briggs and Stratton, Craftsman, Honda, Kawasaki, Kohler, MTD, Tecumseh, Toro, Walbro, and more. Enter the full model number of your lawn mower, or the mower’s engine, in the Repair Clinic website search bar to see a complete list of comparable parts. You can then narrow that selection by using the “Part Category” filter (Examples: “Dipstick”, “Carburetor”) as well as the “Part Title” filter (Examples: “Dipstick Tube”, “Choke Valve”) to identify the specific part that works with the engine. While you’re on the Repair Clinic site, you can do a little exploring to find “how-to” videos, articles, and diagrams to instruct you on how to replace the part yourself.

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