What Kind of Oil for a Murray Select Lawn Mower 22 4.5 HP

Thick or Thin Oil

• Before you find oil for your Murray 4.5 horse power engine, you must understand viscosity ratings. Viscosity is the speed that oil will activate and cycle throughout your Murray’s engine. The lower the number in front of the “W”, the thinner the oil. Thin oil is great for winter use but it’s not good to withstand hot temperatures for very long. There are also multi-viscosity oils that activate depending on ambient temperature.

Recommended Weight

• Since your Murray mower uses a Briggs and Stratton engine, there are specific recommendations for when to use designated oil weights. You can use 10W40 synthetic oil for nearly all ambient temperature operations. For warmer air temperatures -- 46 degrees Fahrenheit and above -- utilize SAE-30 weight oil. Select 10W30 if you use your mower during summer and winter months from 6 to 122 degrees F. For primarily winter use- below 46 degrees- use 5W30.

Conventional Oil

• The Murray 4.5 Horsepower engine was built to conventional oil specifications. Conventional oil is petroleum-based and relatively inexpensive. However, there are additives and contaminants, such as wax that aren’t removed from conventional oil during the refining process. This subjects your engine to sluggish performance if you don’t change conventional oil regularly. You also have to dispose of conventional oil carefully since it is also a pollutant.

Synthetic Oil

• Synthetic oil is usable in your engine. It’s created in a lab under controlled conditions to mimic conventional oil with added benefits, such as withstanding a higher temperature range. There are also more cleaning agents of uniform molecule size in synthetic oil. However, synthetic oil can cost three times more than conventional oil. It’s also not recommended for new engines when compared to conventional oil because it doesn’t coat the moving parts as well. If you will switch to synthetic oil, do so after 50 operating hours.