Everyone knows that lawnmower maintenance is the gateway to becoming a lifelong gearhead. Skills learned while changing your lawnmower’s spark plugs or engine oil relate directly to the skills needed to change those items in your car. However, your vehicle usually carries its owner’s manual in one storage compartment or another, but your lawnmower’s manual may be lost forever. So how do you know what oil to use?

Is your lawn mower a two-stroke or four-stroke?

Before shopping for engine oil, you’ll need to know if your lawnmower engine is a two-stroke or a four-stroke, often called two- or four-cycle. You probably already know this, even if you don’t realize it. Typically found only on small lawnmowers, weedeaters, and chainsaws, two-stroke engines use oil mixed into their gasoline, which provides engine lubrication. Four-stroke engines power most walk-behind and riding lawnmowers and use plain gasoline. Like most gasoline-powered cars, four-stroke engine oil remains in a reservoir at the bottom of the engine to provide lubrication. 

Conventional vs. synthetic lawn mower oils 

Choosing between conventional and synthetic oils is often a matter of preference. In most cases, conventional oil keeps lawnmowers operating smoothly over their expected life. However, lawnmowers that see commercial usage or extreme heat environments may reap the benefits provided by more expensive synthetic oils. In either case, Bob Vila says that “the quantities involved are modest, so some owners choose to use synthetic oil anyway.”

SAE-30 or 10W-30

An oil’s viscosity is a measure of its thickness. For example, a syrup is more viscous (thicker) than water, just as 30-weight is more viscous than 10-weight. As oil gets hotter, it becomes less viscous, and its viscosity increases as it gets colder. 

Multi-weight oils such as 10W-30 offer flexibility over an extensive temperature range experienced by cars driven in various seasons. As lawnmowers usually operate during relatively stable warmer temperatures, single-weight oils are the most used, with SAE-30 being the most popular. 

Bob Vila’s picks for the best oils for lawn mower maintenance

Bob Vila’s four-stroke oil recommendation is STP’s synthetic SAE-30 4 Cycle Oil. This offering from STP features antioxidants to prevent oil degradation at high temperatures, detergents designed to avoid carbon buildup inside the engine, and rust inhibitors to protect the engine’s internals during storage between mowing seasons. 

The best two-stroke oil on the list is HP SYNTH 2-CYC OIL from Husqvarna. While the name suggests that this oil is synthetic, it is a synthetic blend that “offers many of the performance advantages of full synthetics,” according to Bob Vila. In addition, it comes in a convenient six-pack, with each 2.6-ounce bottle providing enough oil for a 50:1 ratio when mixed with one gallon of gasoline. 

Bob Vila’s pick for “Best Bang for the Buck” is Briggs & Stratton 2-Cycle Easy Mix Motor Oil. As a conventional oil designed for two-stroke engines, Briggs & Stratton’s Easy Mix Motor Oil comes in a 16-ounce bottle with a “convenient measuring section built into the top.” In addition, the formula features a fuel stabilizer that allows low smoke operation, results in less spark plug fouling, and provides smoother running engine operation.