What Weight Oil to Use in a Mulching Lawnmower

What the numbers mean

• Motor oil containers display numbers such as 10w/30 and SAE 30. These numbers measure the viscosity, or how fast motor oil flows through an instrument called a viscometer. The "w" in 10w/40 indicates that the oil was tested at cooler temperatures than oil marked without the "w," such as SAE 30 or 10/30. The "w" signifies winter, or cooler than usual running temperatures. Motor oil is generally tested for viscosity at about 210 degrees Fahrenheit, which is about the temperature of a running car engine. The advantage of using motor oil designated "w" is its ability to perform at the same viscosity rate whether the engine is cool or warm. This reduces the need for dry running and promotes even distribution of the oil through the engine.

Lawnmower Lubrication

• Motor oil lubricates the engine of your mulching lawnmower. The higher the second number or number appearing after SAE, such as SAE 40, the thicker the motor oil. Motor oils are designed for protecting the moving parts of larger engines for cars and trucks; the thicker the oil, the more protection it provides. Lawnmower engines are smaller and don't run as often or consistently as vehicle engines; using motor oil with lower ratings provides sufficient engine lubrication.

Lawnmower Oil Change

• Manufacturers typically recommend changing your lawnmower's oil once a year at the beginning of the mowing season. Changing the oil before you mow for the first time each season ensures that your mulching mower's engine receives optimum protection with fresh oil. Getting in the habit of changing the oil at the beginning of the mowing season also prompts your memory for changing the oil on time.

Maintaining Mulching Mowers

• Keeping your mulching lawnmower in top shape ensures proper mowing and can prevent damage to your mower and lawn. Check the oil bi-monthly; if you're mowing large expanses of lawn or mow frequently, change your lawnmower's oil when it becomes dirty. Sharpen the blade once a month and remove all caked grass from under the lawnmower after each use. When storing your mulching lawnmower for the winter, clean it thoroughly and remove the gasoline from its tank. It's okay to put the unused gas from your mower into your car; this solves the problem of disposing of unused lawn mower gas, which destabilizes after sitting for several months.