Engine oil is crucial to the healthy operation of any motor vehicle. To run correctly, engines need a precise amount of oil. Too little oil doesn't provide enough lubrication for the engine, and too much has its share of problems, too.
As engine oil heats, it expands. When your engine is filled with exactly the right amount of oil, the expanded oil fills the engine components, keeping everything lubricated. If your oil is overfilled, the oil will expand and put extra pressure on the gasket in your oil filter. If the engine runs long enough, the pressure on the gasket will cause it to fail, and the vehicle's oil will leak.
When your engine's crankshaft is overfilled, the crank will whip up the oil as it spins, causing the oil to foam. As the foamed oil passes through the engine components, it does not lubricate effectively because it is full of air. When your engine isn't getting the lubrication it needs, it will eventually overheat and, if left unresolved, can even seize.
If you think you've filled your oil reservoir too much, check it with the dipstick. If the oil is reading too high, let the engine cool and check the level again. When the oil cools, it contracts and you may have the correct amount. If not, unscrew the drain plug on the bottom of the vehicle's oil pan and drain some oil into a bucket. Check your oil level again and top it off if necessary.