* Crankshaft damage: Excess oil can froth and create excessive pressure in the crankcase, leading to foaming and aeration of the oil. This reduces its lubricating properties and can damage the crankshaft and other engine components. The increased pressure might also interfere with the crankshaft's rotation.
* Oil pressure problems: The oil pump might struggle to handle the extra volume, potentially leading to low or inconsistent oil pressure. Low oil pressure can cause engine damage, and some vehicles have sensors that will prevent starting if the pressure is too low.
* Damage to seals: Excess oil can leak past seals and gaskets, leading to oil leaks and potential damage to other engine components.
While a very slight overfill might not immediately cause problems, a substantial overfill will almost certainly prevent or severely hinder starting. It's crucial to always check your oil level using the dipstick and fill to the recommended level.
