Constantly overfilling oil in an engine will result in damage to the internal components. The oil will not circulate correctly, leaving many of the moving components dry.
Crankshaft and Connecting-Rod Damage
If the crankshaft contacts the oil while it is rotating, foam will form. This foam will not allow the oil to lubricate the internal components. Too much oil leads to oil starvation, which results in broken crankshafts. Another issue occurs when the connecting rods, which mount directly to the crankshaft, do not receive proper lubrication. The oil starvation leads to rod knocks, which occur when the bearing that seats the connecting rod breaks loose.
Rising Oil Levels
There are other ways in which the oil level increases without user error. When the oil level is checked and is higher than its previous level, the additional fluid may be due to coolant or condensation or fuel, both problems that require immediate repair. Even if there is a mixture of oil and other fluid, lubrication problems are still possible. Coolant leaks usually mean there is a problem with the head gasket. If not repaired, the engine can warp and cause permanent damage. Fuel can point to issues with injector or pump seals. Fuel loss will result until the issue is repaired.