Topping off the oil in a vehicle to the point that it overflows can cause the additional oil in the oil pump to build pressure on the seal on the rear main bearing. As a result, the pressure on the rear main bearing can burst or rupture, ultimately causing oil to leak from the vehicle.
In addition, the oil leaking may cover the front bay of the engine, traveling from the oil filter to the clutch and possibly all the way to the brake disks. Leaking oil can cause a froth on the engine, which can seep into the bearings of the vehicle. When this happens, the driver may notice smoke spewing from the engine or a burning smell while driving the vehicle.
To avoid overfilling the oil in a vehicle, allow the vehicle to sit overnight, preferably in cold temperatures, so that the oil can settle back into the sump. If the vehicle is warm, it is best to let it sit for at least 30 minutes. Ensure the vehicle is on level ground before pulling the dipstick out of the oil compartment. Wipe the excess oil from the dipstick, reinsert it, and pull it out again to check the level. When refilling the oil, stop before reaching the max level on the dipstick.