It is highly recommended to use Briggs & Stratton synthetic 5W-30 oil, because the oil has high performance in all temperature ranges. Using this detergent oil is also a form of compliance to Briggs & Stratton warranty requirements.
Other engine oil types include SAE 30, which is good for warmer temperatures of 40 degrees Fahrenheit or higher, and SAE 10E-30, which works best between 0 and 100 degrees Fahrenheit.
Choose the right oil type by first identifying the lawn mower, because the recommended mower oils depend on the manufacturer of the engine. As such, use the engine manual to identify the lawn mower.