If you’ve heard the term “well-oiled machine” before, know that it applies to your riding lawn
mower. Like any machine with an internal combustion engine, a mower needs motor oil. The
lubricating and cooling action of oil prevents your engine from overheating -- and keeps you from
having to replace your mower because of a ruined engine.
But before you change the oil on your mower, be sure you know what oil type is right for the
engine. Finding the right motor oil will depend on a variety of factors.
Types of Mower Engine Oil
What separates one motor oil from another? Grades, which are based on viscosity and how the
oil behaves at different temperatures. Lawn mowers typically feature either a two-stroke engine
or a four-stroke engine. The latter is much more common and means that the engine burns
straight gasoline, while also requiring motor oil to be added separately. Two-stroke engines burn
gasoline and oil at the same time, so the two are mixed together before going into the tank.
The grades are as follows:
- Single Grade Oil contains no additives.
- Multi-Grade Oil uses additives to provide better viscosity across a range of temperatures.
- Synthetic Blend Oil is a mixture of regular and synthetic oil blended with additives to boost performance in colder temperatures.
- Full Synthetic Oil is an artificial lubricant designed for use in high-performance and commercial engines.
Motor oil suitable for cars and trucks is generally suitable for your mower, so long as it has a
four-stroke engine. A better match for a two-stroke lawn mower engine would be motor oil
designed for the engines in chainsaws, water pumps, and weed eaters. But you should also
check for a service rating (i.e. SF, SG, SH, SJ, etc.). The higher, the better.
Choosing the Best Oil for Your Lawn Mower
Determining the right motor oil for your lawn mower means finding the best oil for work in your
climate. Different types of oil perform better at certain temperatures than others.
- SAE 30 is the most common type of oil for small engines and is best suited for work under warmer temperatures.
- SAE 10W-30 has a much wider temperature range than SAE 30 and can improve cold-weather starting, though that may lead to a greater consumption of oil.
- SAE 5W-30 is your all-purpose motor oil, providing protection at all temperatures without having to consume greater amounts of oil at starting.
- Synthetic SAW 5W-30 is for working under very cold temperatures.
- Vanguard 15W-50 is another type of oil with a wide temperature range and it is ideal for continuous uses such as commercial lawn cutting.
How Often to Check and Change Lawn Mower Oil
If you have a mower with a four-stroke engine, you should be checking the oil level each and
every time you take it out to mow. If it is a brand new mower, be sure to change the oil after the
first three to five hours of use. There may be tiny metal filings in the oil from the internal
movement of parts, so it is best to flush them out before they can cause excess wear.
For regular use, change the oil in your walk-behind mower at least once a season or every 50
hours of use. The same holds true of riding mowers, though for 100 hours of use, rather than 50.
Consult the owner’s manual to find out how much oil is required.