The Down 'n Dirty on Motor Oil For Your Push Lawn Mower
Your mower puts in long hours in one of the dirtiest, dustiest environments imaginable. And like any other internal combustion engine, it relies on motor oil in the crankcase to keep everything lubricated.
While it's easy to forget about the motor oil that's in your mower, it's not a good idea. All of its dirt and contaminants can cause a buildup of sludge and carbon on bearings and other parts and will wear down your engine. You don't neglect oil changes in your car for that very reason; why do so in your mower?
What's the Best Motor Oil For Your Mower?
The good news is, you don't need a special motor oil for your lawn mover—ordinary automotive motor oil will do. (NOTE: This does not apply to weed-wackers or other lawn care equipment that use a two-cycle engine and needs an oil/gas mixture. They should only be used with a specially-formulated two-cycle oil.)
For most applications, straight 30W or a multi-grade motor oil such as 10W-30 will work just fine. If you are in an extremely cold area, you might consider a thinner viscosity multi-grade motor oil such as 5W-30. A thinner oil can circulate through the engine more quickly in cold weather, whereas thicker oil might become more viscous in extreme cold.
Just make sure the motor oil you choose is of good quality with an SF, SG, SH, or SJ rating and that it's a detergent motor oil. There's no need to use any kind of additives—straight motor oil will be fine.
Can I Use Synthetic Oil In a Mower Engine?
The answer to that one is an unequivocal yes. A small engine can get all the same benefits from synthetic oil as an automotive engine.
Synthetic oil is more stable across a wide range of temperatures and won't thin out in extreme heat or thicken in cold weather like conventional oil. It also offers better engine protection all the way around and can go for longer intervals between oil changes.
Still, considering how dirty a mower's working environment is, it's a good idea to change the oil at the beginning of the season even if it's a synthetic.
Changing the Oil in Your Lawn Mower
This is going to be a pretty simple task, since lawn mowers generally don't have oil filters nor a drain plug. Start the mower and let the engine run for about 60 seconds to circulate any sludge and dirt that might be in the oil (rather than leaving it in the bottom of the crankcase). Tip the mower over on its side and remove the filler plug and dipstick.
Let the oil run out until the crankcase is empty, then refill. Be sure to drain it into an oil-safe drain pan, and don't let any used oil drain onto the ground. Dispose of the old oil properly.
Most one-cylinder mower engines will require about a quart of oil. Check the oil level with the dipstick, and you're ready to go with a crankcase full of the correct oil for your mower.