What Weight Oil for a Lawn Mower?

Oil Weight and Viscosity

• To understand oil weight, you have to understand viscosity. A viscosity rating indicates the speed at which oil will start flowing at a given temperature. Lower-rated oils are thinner and will flow faster into the engine on start up. However, they do not operate as well when temperatures reach higher ranges. Conversely, a higher viscosity rating means a thicker oil with slower flow but greater high temperature capacity. Synthetic oils and multi-viscosity oils have the advantage of changing their flow rate according to the ambient temperature.

Ambient Temperature

• With an understanding of viscosity, you can now choose the oil weight based on the ambient temperature. If your mowing in a colder climate of 40 degrees Fahrenheit or below, it is generally recommended to use 5W30 weight oil. For warmer temperatures of 46 degrees and above, use SAE 30. 10W30 is more versatile and can be used for temperatures 6 degrees F and above, while 5W30 synthetic oil can be used for all temperature ranges.

Conventional Oil

• Conventional petroleum oil is acceptable to use in a lawn mower engine. Conventional oil is relatively inexpensive and can be sold in various units, from a handful of ounces to 55 gallon drums. This type of oil is appropriate for coating engine parts, which helps reduce friction between them. The disadvantage is that conventional oils can be harmful to the environment if not disposed of properly. Conventional oil also burns up over time, emitting pollutants in the air. This consumption can also result in more frequent oil changes and replacements.

Synthetic Oil

• For environmental purposes, synthetic oil can be used in your mower. Synthetic oil is created out of special chemicals in a lab so that it mimics conventional oil with less toxic environmental implications. Synthetic oil also doesn’t burn up as quickly, reducing the possible air pollutants when mowing. This also reduces the amount of time you’ll need to change or refill your oil. However, synthetic oil can also cost three times as much and doesn’t coat engine parts as well to reduce friction.