Changing Oil in 4-Cycle Engines

The way to make a four-cycle engine last a long time is to change the oil regularly. Oil that is in too long (usually, more than 25 operating hours) gets dirty, begins to break down, and causes rapid engine wear (particularly on the piston rings, which hold oil tightly in the cylinder). Then oil begins to leak into the combustion chamber, resulting in poor performance. It’s quite simple to change oil.

Consult the owner’s manual for the locations of the drain and filler plugs for your lawn mower or other equipment. On lawn mowers, the oil drain plug is often under the housing, near the blade, although on some models it may be on the side of the engine, near the bottom.

Spray the engine with water to rinse off dirt, keeping the water off the shroud and fins. Be sure to clean around the opening where the oil is added. Then run the engine for a few minutes—warm oil flows better, and more of the old oil will flow out. Remove the plug with a wrench, and then let the oil drain for at least 10 minutes (20 minutes is better). Replace and tighten the plug. Now you are ready to put in the new oil.

Use the type specified in the owner’s manual. If you don’t know what type to use, try a good 30-weight oil—it’s generally safe. Always use a funnel to prevent spilling oil on the engine or the housing; spilled oil would soon collect dirt and keep the engine from being properly cooled.

Remove the oil filler-plug and pour in the oil. The oil level should be near the bottom of the threads on the filler plug when the plug is tightened down. If the engine has a dip stick, use it—the instructions for your piece of equipment will tell you what oil level to maintain. Do not overfill.