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Q: I haven’t changed my lawn mower’s oil since last season, so I’m feeling rusty. Remind me: What type of oil can I use in my lawn mower?
A: You’re not alone. In fact, this bit of lawn mower maintenance happens so occasionally that some people forget to replenish lawn mower oil in the first place. It needs replacing after every 20 to 50 hours of operation, depending on your mower’s specifications. If your yard is small, that might mean as few times as once a year! But, while this task is infrequent, it’s also important to change the oil properly—starting with the correct type of oil for lawn mowers—to keep your machine running.
Two types of oil can go into operating lawn mowers, but your mower’s size, type, and capacity might help determine which of these two is the better option. Even the climate you live in can make a difference when the time comes to change or add oil, since each type of oil for lawn mowers has its own recommended temperature range. If you live in a place that frequently heats up to more than 100 degrees, for example, it might be wise to choose an oil made to withstand a wide range of temperatures.
Different Kinds of Lawn Mower Engine Oil
According to a survey of consumers conducted by Briggs & Stratton, the world’s largest producer of gasoline engines for outdoor power equipment, 48 percent of those who buy automotive oil for their mower believe that automotive oil and small engine oil are one and the same.
In fact, lawn mower engine oil (as well as oil for other small engines) might actually be the only type your mower can tolerate. Using motor oil meant for a tractor or car can clog and disable some units completely due to its higher viscosity.
Always check your manufacturer’s specifications first. No owner’s manual handy? If yours has a Briggs & Stratton engine, you can use the company’s interactive tool to determine the best oil for your specific lawn mower’s engine based on its make and model, motor type, and local climate. Talk about a shortcut! Otherwise, at a minimum, it’s important to keep a few guidelines in mind.
Lawn Mower Oil Types
Not all oils are equal, and it helps to get to know the subtle differences to determine the best oil for a lawn mower and avoid a costly mistake. In general, there are two main types of oil: motor oil and small-engine oil. Brands vary in their formulas, with some being regular oil, some a mix of regular and synthetic and some fully synthetic. Older oils typically were one weight or grade only, but newer oils have a viscosity rating added.
- SAE 30 is a single-grade, or straight weight, oil with a viscosity rating of 30 and is safe for small, air-cooled engines, typically older models.
- SAE 10W-30 is a multigrade engine oil that can work in cold temperatures, as well as hot, for a fairly balanced temperature range.
- SAE 5W-30 is a multigrade engine oil with a low viscosity to flow better at colder temperatures (than 10W-30), but protect the engine enough in heat.
- Synthetic SAE 5W-30 is a synthetic (artificial) lawn mower oil that works for both cold and warm weather. Synthetic oils tend to be more stable across temperature ranges than conventional oils.
- Vanguard 15W-50 is a brand of fully synthetic engine oil designed for commercial applications that operates at temperatures ranging from 20 to 130 degrees.
Motor Oil SAE Viscosity Grade
The Society of Automotive Engineers (SAE) grades motor oils by viscosity. Viscosity loosely relates to weight, or thickness, and more accurately as a measure of how the oil flows at specific temperatures. In colder temperatures, thinner single-grade oil performs better in engines.
It gets a little more complicated with multigrade engine oil. Look at the first number, with a W (10W, for example) as a measure of flow in cold temperatures. The W stands for winter (not weight). The lower this number, the less viscosity an oil will have at colder temperatures, and the better it will flow. Too thick when the engine starts, and it won’t flow through and protect those critical engine components.
The higher number that follows (the 30 in 10W 30) refers to viscosity at higher operating temperatures and in hot weather. Multigrade oils typically are designed to flow in a range of temperatures to match conditions. Some oils have additives that also keep viscosity steadier in cold or heat.
How to Choose the Best Oil for Your Lawn Mower Engine
When choosing the right lawn mower oil type for your mower, your best bet is to check the manufacturer recommendations. Also consider the engine type (such as 2-stroke engine), oil viscosity, and average temperatures where you live.
Motor Oil for Four-Stroke Engines
Four-stroke engines tend to power heavy-duty equipment, but are reliable and your best bet for larger lawns. These engines are common in large and/or riding lawn mowers as well as some push mowers. Even so, be sure to check your manufacturer’s manual or website for specific instructions on which grade of motor oil to use, since—much like a car—the engine might be sensitive to certain additives.
Oil and gas are kept separate in a four-stroke engine. Oil with a grade of SAE-30 is often a safe bet, but it’s still worth confirming since a lawn mower is no small investment. You can buy SAE-30 motor oil online (view example on Amazon), at any auto parts store, from most gas stations, and in the automotive section of a hardware store.
Small Engine Oil for Two-Stroke Engines
This type of engine is most commonly found in smaller and older push mowers, plus other small engines, like on weed trimmers and chainsaws. Its popularity as a preferred lawn mower engine has decreased some over the years as four-stroke units have become more common. Louder and smokier than their four-stroke counterparts, two-stroke motors can keep running no matter how steep an angle you’re trying to tackle (think: hilly or sloped terrains).
Two-stroke engines are lighter and cost less, too. And, since they use the same fill port for both gasoline and small engine oil, two-cycle motors require owners to mix them together in a specific ratio such as 32:1 or 50:1—refer to your operator’s manual for the correct gas-to-oil ratio.
These oils typically have additives to help clear carbon deposit and minimize wear, among other tasks. Find small engine oil online (view example on Amazon) or in the lawn and garden section of any hardware or auto parts store.
Know when to change your lawn mower’s oil.
A brand new mower might need an oil change after the first 5 hours of use; refer to your unit’s manual. Beyond that, small motors might need an oil change every 25 hours of use or thereabout, while larger motors typically can last up to 50 hours before requiring oil replacement.
A handful of factors can increase the frequency of oil changes, including extreme dust and dirt, rough terrain, frequent mowing of wet or muddy grass, and even a hot climate—conditions in which the engine is forced to work harder. If you have a large yard (or if you mow a small yard frequently), use a dipstick or clean cloth to check the lawn mower engine oil level before each use once it’s run beyond 20 hours or so.
Even if the mower hasn’t hit the 20-hour mark at the end of a season, make a point of changing your oil each spring, before your first mow. Avoid overfilling the mower by checking the oil level with a dipstick.
FAQ About Lawn Mower Oil
What kind of oil do you use in a lawn mower?
The oil type depends on the engine type, typical operating temperatures, and especially the recommendations of the lawn mower manufacturer. In general, small-engine oil that is a mix of oil and fuel works in two-stroke engines, and straight oil typically works for four-stroke engines. Factors such as temperature affect which grade to choose.
Can you use regular motor oil in a lawn mower?
Lawn mowers with four-stroke engines might do fine with regular motor oil, but always check the manufacturer documentation to make sure. Some automotive oils are too high in viscosity and meant for larger engines, so don’t assume that more is better. Many deluxe models of push mowers and riding mowers use regular motor oil. Two-stroke engines cannot use motor oil; they need a mix of fuel and oil specially designed for small engines.
What’s the best oil to use in a lawn mower?
The best oil to use in a lawn mower is the one recommended by the manufacturer. Viscosity and whether the oil is synthetic or regular oil can vary based on climate, conditions, and engine type.
Can I use 10W30 instead of SAE 30 in my lawn mower?
No, it is not recommended. Most engines that call for SAE 30 are older models of mowers with engines designed for straight weight oil. These models were designed before multigrade oil became available, so you should not substitute with the multigrade option.
Final Thoughts
Lawn mower oil is essential to keeping your mower running efficiently and effectively, and use of the right oil, plus regular oil changes, can protect the life of the mower’s engine. Take the time to find out the best oil for your lawn mower based on the mower’s model and recommendations of the manufacturer. Also consider operating conditions, viscosity, and type of engine.
A little prep avoids irreversible damage caused by forcing the wrong oil through your lawn mower’s engine.
