Briggs and Stratton has been in business since 1908 and is currently the world's largest producer of small, air-cooled gasoline engines. The company has gained a reputation for producing reliable small engines in a variety of sizes. Several models of 4.5 horsepower engines have been produced over the years, and these are commonly found on various brands of rotary lawn mowers. Regular maintenance is essential to the trouble-free operation of all small engines, especially when used under harsh conditions. Regular oil changes are a key part of any preventative maintenance program. The novice mechanic can save time and money by learning how to change the engine oil.
Perform the oil change with the engine warm. Allow the engine to heat up to operating temperature, and then allow to cool for 5 minutes or so before continuing. Warm oil flows much better than cold oil so this step will allow the old oil to drain more completely. Be careful not to touch hot engine parts.
Turn the mower on its side with the air filter side or spark plug side up.
Locate the oil drain plug on the bottom of the motor. Position an oil catch pan directly below the drain plug. Remove the drain plug by rotating counterclockwise. Depending on the engine model, the drain plug may require a wrench, a hex wrench, or a 3/8 inch drive socket wrench and extension in order to turn it.
Allow the old oil to drain, taking care to catch all of the oil in the catch pan. Reinsert and tightened the drain plug by twisting clockwise and tightening with the same wrench/hex wrench/socket drive as you used to remove the plug. Turn the mower back to the upright position. Dispose of the old oil in accordance with local regulations.
Pour in the correct amount of the approved type of oil for the engine, as specified in the owner's manual. If in doubt, use 10W-30 oil in cool climates and SAE 30 weight oil in warmer climates. Add the oil a little at a time until a check with the dipstick shows a level just below the full mark.