It is very important that you change the oil in a Briggs & Stratton four-cycle engine to keep it running at peak performance. Regular oil changes will increase efficiency, reduce emissions and reduce wear and tear to increase the engine’s useful life. You should change your oil at least once per season following some basic steps.
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Look the engine over to see if it has an oil drain plug. If it doesn’t, you will have to turn the mower over on its side to empty the oil from the crankcase. Drain the fuel tank so gasoline doesn’t spill over you and the engine when you’re dumping the old oil. Disconnect the spark plug so the engine doesn’t accidentally start if you move the mower blade.
Determine whether the engine has an oil drain plug, or if the oil must be drained by turning the mower over. Most push mowers have no drain plug and will need to be turned over to empty the oil. Unscrew the drain plug or fill cap and drain the old oil into an oil pan. Tip the mower away from the side of the engine where the air filter and carburetor are located to keep oil out of them.
Let the oil drain for a minute or so until you are sure the old oil is out of the crankcase. You’ll only be able to get about 75 percent of the oil out. The rest will cling to the inside of the engine.
Check the owner’s manual for your engine to determine what oil is right for your mower. Most Briggs & Stratton engines use SAE30 four-cycle small engine oil. Be careful not to use multi-grade oils not recommended for your engine. These can damage your engine or cause excessive wear on moving parts if the oil is too thin. Trust the manual. Total capacity of most small engines runs around 20 oz. This is total capacity, not what you need to change your oil (remember a fourth gets left behind.
Add about 10 oz. of new oil back into the oil reservoir. After that, add a couple of oz. at a time and check the level with your dipstick as you go. If you go over the top fill line on the dipstick, the mower will burn and smoke a great deal until it burns off the excess. Don’t worry if the next time you change the oil, it has turned brown. This is normal. The old oil (remember that 25 percent left behind) has mixed with the new oil.