The Best Type of Oil for a Lawn Mower

The SAE 30 grade is standard, but not the same as SAE 10W-30

Gas Powered Lawn Mower Oil

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Do you need to know what type of oil a lawn mower uses? Most gas-powered lawn mowers operate with 4-cycle engines. All gas-powered engines need sufficient oil to run smoothly and they take the same type of oil to run as do cars. There are many brands of oil to choose but your first consideration is the type of oil that works best for your mower.

Choosing Lawn Mower Oil By Engine Type

Adding oil to a 4-cycle engine is an entirely different process than for a 2-cycle engine. 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 of lawn mower oil to choose from:

  • Conventional
  • Synthetic blend
  • Fully synthetic

The best oil to use depends on the type of equipment you're using, the engine, and the temperature outside.

There are a few 2-cycle lawn mowers still on the market, and this type of engine also runs other gas-powered yard equipment, such as weed-eaters and hedge trimmers. A 2-cycle mower has 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.


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 overnight. 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.

Lawn Mower Oil Types: Pros and Cons

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 used 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 or as easy to find as conventional oils, specifically for lawn mowers. 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 that have undergone a higher degree of refinement than crude oil.

Many of these types are blends that 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 fully 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.

Lawn Mower Oil: Climate Factors

Some manufacturers claim that synthetic oils break down more slowly than conventional oils. However, regardless of the 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, 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
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  1. What Type and How Much Oil for My Lawn Mower? Briggs & Stratton.