One can purchase parts for a used Briggs and Stratton lawn mower from the following sources: Mower Graveyard, eBay, Briggs and Stratton, Zangler Repair, Lowes, Discount Online Parts.
You can find the operator's manual for that engine at www.briggsandstratton.com. You will need to contact the manufacturer of the mower for the lawn mower owner's manual. Briggs and Stratton did not amke that mower, only the engine.
It is a 2-cycle 4HP Briggs motor.
Check the underneath of lawn mower for grass built up.
go to briggsandstratton.com
SAE 30 weight full synthetic oil.
Briggs and Stratton is a select brand of lawn mower. When oiling one's Briggs and Stratton lawn mower engine, it is best to use a high quality oil. One can find such an oil at their local home improvement store, such as Home Depot.
Briggs and Stratton and Kohler engines are considered quality components. Neither is likely to be better. However, the Briggs and Stratton brand is more popular.