When you start up your Murray lawn mower, oil doesn’t always flow automatically through the engine parts. Viscosity ratings on your oil will indicate how fast or slow the oil flows, depending on the ambient temperature. A low viscosity rating like 0 or 5 in front of a "W" means that the oil is thin and will flow quickly. However, it doesn’t operate as well at higher temperature ranges. Higher numbers indicate a thicker oil that flows slower yet handles higher operating temperatures. If you operate your mower during varied temperatures, consider using multi-viscosity oil, because it can change its flow rate accordingly.
Murray mowers use Briggs and Stratton engines, which have oil-weight requirements for use depending on the ambient temperature during operation. If you are mowing or using a snow plow attachment at colder temperatures, use a lower-weight oil like 5W30. For operating at a varying temperature range 6 degrees F and above, use 10W30 weight. For strictly warmer temperatures above 46 degrees F, SAE 30 is recommended. Otherwise, use 5W30 synthetic oil, which can be used at all operating temperatures.
The Briggs and Stratton engines are designed to use conventional engine motor oil. This type of oil is relatively inexpensive and comes in a variety of weights, making it adaptable to your Murray mower’s needs. Many oils have multiple viscosity ratings, which means you can use it at both high and low temperatures. But since conventional oil can be toxic to the environment, you must ensure it's disposed of according to your local environmental regulations.
You can use synthetic oil on your Murray mowers instead of conventional motor oil. There are specific environmental advantages such as reduced pollutants from the exhaust when using synthetic oils. Synthetic oils also last longer in your mower than conventional oil, and deposit relatively fewer sediments during storage. If you plan to use your mower during multiple temperature ranges, synthetic oils could be to your advantage. However, they can cost up to three times as much as conventional oil.