What Kind of Oil Do You Use in a Lawn Mower?

Gas Powered Lawn Mower Oil

Hobo_18/Getty Images

Power equipment means less physical effort when it comes to maintaining your property. Weed-eaters, hedge trimmers, rototillers, and pole trimmers often are powered by 2-cycle engines. But the piece of equipment that gets the most wear and tear is your lawn mower and, with a few exceptions, gas-powered mowers operate using 4-cycle engines.

All gas-powered engines need oil to run smoothly and to lubricate parts that will get damaged without it. Running your gas mower without sufficient oil is the quickest path to the junkyard. There are many different brands of oil to choose but your first consideration is the type of oil that works best for your mower.

2-Cycle Engines vs. 4-Cycle Engines

Adding oil to a 2-cycle engine is an entirely different process than for a 4-cycle engine and there are a few 2-cycle lawn mowers still available to homeowners.

2-cycle mowers have one tank that holds a combination of gas and oil usually premixed by the homeowner. Information in your owner's manual will offer recommendations about which 2-cycle oil to use. They are usually lighter weight synthetic blends often labeled as performance or high-performance.

Lawn mowers with 4-cycle engines have two tanks-one for gas and one for oil, each added separately. 30 weight oil, the same used in many automobiles, is the most common weight used in lawn mowers. Weight refers to the viscosity or thickness. There are three types to choose from; conventional, synthetic blend, and fully synthetic with pros and cons for each. The best oil to use depends on the type of equipment you're using, the engine, and the temperature outside.

Tip

Labels offer information about the weight and type of oil that make up the product. If you are unsure about the weight or type of motor oil you have, try this home test. Place the oil in your freezer over night. If it pours more like water, it is likely a synthetic or lower weight oil such as 5w30. If it pours like molasses, it is probably a conventional oil like SAE 30,

Choosing Oil for Mowers with 4-Cycle Engines

Briggs and Stratton, a manufacturer of small engine equipment, recommends choosing a high-quality detergent oil classified as "For Service SF, SG, SH, SJ" or higher." Avoid using any special additives with these oils. The product label should also indicate whether the oil is synthetic or conventional.

The classifications of SF through SJ are issued by the American Petroleum Association (API), and are significant mostly for automobiles. The letters identify the best oils for automobiles manufactured during a certain time period and cover a much wider range for lawn mowers.

Conventional Oil

Conventional oils are mineral-based products refined from crude oil taken from the ground. The greatest advantage is cost which is often about half the price of synthetic oils. Even with increasing popularity, synthetics often aren't as available and easy to find as conventional oils. The age of your mower may be another reason to choose the older standard. While both types will work perfectly fine, your older engine may not be built to take advantage of synthetic oil and this can add up to unnecessary expense with little benefit.

Full Synthetic Oils and Synthetic Blends

Synthetic oils are laboratory created and developed using petrochemicals which have undergone a higher degree of refinement than crude oil.

Many of these types are blends which use conventional oil as a base. Further refinements are added to develop a product more exacting for specific applications. These applications may include high performance automobiles and high-use gas-powered equipment such as lawn mowers used in commercial landscaping.

The difference between full synthetic and synthetic blends is dependent on the quality of the base oil used to create the product. The most pronounced difference between synthetic and conventional oil is the additives that make up synthetic oils. These include protection and better performance during temperature extremes, longer breakdown time for oil, and slower build-up of sludge and debris caused by impurities.

Choose, Check and Change Your Lawnmower Oil

Some manufacturers claim that synthetic oils break down more slowly than conventional oils. However, regardless of breakdown rate, you should change your lawn mower oil according to the timetable given in the owner's manual.

Checking the level of oil in your mower should be part of the preparations you make every time you mow. Lawn mowers are built to be workhorses and can take a lot of use but it only takes one time for major damage to occur if you neglect to add oil when it's low.

Temperature is also a factor to consider when choosing the best oil. Learn which one to choose for your climate.

  • SAE 30: Warmer temperatures, most common oil for small engines.
  • SAE 10W-30: Varying temperature range, this grade of oil improves cold-weather starting, but may increase oil consumption. 
  • Synthetic SAE 5W-30: Best protection at all temperatures as well as improved starting with less oil consumption.
  • SAE 5W-30: Very cold temperatures.
  • Vanguard 15W-50: Varying temperature range. For continuous-use, such as commercial lawn cutting or pressure washing.
Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. https://www.briggsandstratton.com/na/en_us/support/faqs/browse/mower-oil-type-and-capacity.html