Every lawn mower requires a constant supply of lubrication to keep the engine from overheating and getting ruined. However, too much oil inside the crankcase can damage the engine and cause many problems. If the lawn mower gets overfilled with oil, the excess amount will need removing before it can mow again.
Check Oil Amount
To prevent overfilling, before you fill the lawn mower with oil, always check your model's operator's manual to find the exact amount of oil required. If you lost the operator's manual, contact the dealer or company the mower was purchased from. Most lawn mowers will require between 16 and 20 fl. oz. of a high-quality engine oil, most often with an SAE 30 classification (30 weight oil).
When adding oil into the crankcase, always remove the oil dipstick and check the reading on the stick. Pay attention to the level of oil, and add any more oil slowly, putting only two to three oz. in at a time.
Remove Excess Oil
With too much oil already in the crankcase, the mower may already need a professional to take it out. However, the operator can unscrew the oil fill tube and drain out as much oil from the crankcase as possible. When dumping oil out, tilt the lawn mower on its side, so that the carburetor always points up; this will prevent any oil from entering the carburetor and combustion chamber. Drain the tank slowly into an approved oil container.
After dumping out the excess oil from the tank, make sure to clean up any oil that may have spilled during the process. Any excess oil outside the tank can enter the carburetor and combustion chamber. When this happens, the engine will immediately start having running issues, and, at this point, a service professional should clean out these areas before running the mower again. Clean up all spills with a rag and a brush, if necessary.
When too much oil reaches the crankcase, the oil sump will overfill and the oil will drown the motion of the crankcase. While this is preferable to no oil in the crankcase, the excess oil must be removed from the crankcase and the sump. If the operator can't remove the excess oil through dumping, the engine will need disassembling to access the oil sump. Common indicators the engine has too much oil includes hard starts, white smoke from the muffler, oil splattering around the muffler and other similar problems.