When a person puts too much oil in their car, they can damage the car by creating a leaking engine. The leaking engine is caused by the additional pressure on the rear main bearing seal.
The additional pressure through the windage in the crankcase and the oil pump can cause the seal to break. Another problem that occurs is that the clutch may become a lubricated clutch due to the excess oil. From here, the front seal can break and then oil will flood throughout the car. This essentially leads to rapid damage throughout the car. The exact amount of damage will vary depending on the amount of excess oil as well as how far the vehicle was driven.
If a person puts too much oil in their vehicle, they will need to avoid driving the vehicle until the excess oil is removed so that there is not any further damage to the vehicle. A mechanic can help with this problem.
To avoid an excess oil problem, a person should be sure to check their oil level regularly and especially after adding oil to the vehicle. Before checking the oil level, make sure that the car has not been driven for at least 30 minutes so that the oil will have settled down and will provide an ideal rating.