If you add a little too much motor oil your engine will be just fine as long as you didn't add over 1/2 a quart of motor oil more than the engine requires.
Adding a 1/2 quart or less of motor oil to your engine will not harm the engine but adding more than a 1/2 quart of motor oil can cause the oil to be churned and aerated and turn the oil into foamy motor oil which prevents proper lubrication of the engines bearings and other parts of the engine.
When changing oil add enough oil to the full mark on the engine oil dipstick and then run the engine for a minute or two and then shut the engine off and let it sit a few minutes and check the engine oil again.
If it still shows full then you don't need to add any more oil but if it is still down below the full mark on the dipstick you should add more oil to it at little at a time and check the oil level again with the dipstick.
Continue adding oil little by little until the dipstick reads full.
An extra half quart of oil will not usually hurt your engine although it's best to drain the excess oil to prevent the engines crankshaft from churning the oil and turning it into foamy engine oil.
A half quart of oil extra in an engine is acceptable, especially for larger engines and is not likely to cause any problems.
I've overfilled my engine with a 1/2 quart many times and my engine has been just fine.
However overfilling your engine by 1 quart is bad and will eventually hurt your engine.
If you overfill your oil by 1 quart the engines crankshaft will start churning the engine oil and then cause the engine oil to become foamy and unable to properly lubricate the engine and eventually lead to engine bearings seizing and even a rod being thrown.
If you overfilled your engine by 1 quart you should drain the extra quart of oil out to prevent damage to the engine.
You can overfill your oil and overfilling your engine will oil can cause damage to the engine.
When the engine has too much oil and is overfilled the oil will get aerated or churned by the crankshaft and will turn the engine oil foamy which makes the oil unable to lubricate the engine bearings and other engine parts as it should.
As a result the engine bearings will eventually seize and/or the engine will throw a rod and be damaged.
If you overfilled your oil by 1/2 a quart or less then it is not always a cause for concern but overfilling the engine more than 1/2 a quart is bad and will damage the engine.
If you did overfill the engine with too much oil you must drain out the excess oil.
If the oil is just foamy or bubbly but it's not discolored and otherwise looks normal then it's a sign that the engine has been overfilled with too much oil.
When an engine is overfilled with too much oil it causes the oil to be mixed and churned and aerated by the crankshaft which causes the foamy appearance of the oil.
If you don't drain the excess oil out to the proper engine oil level it will eventually lead to engine bearing failure and the bearings of the engine will seize up and could even cause the engine block to break or a rod to throw through the oil pan or engine block.
Foamy engine oil cannot lubricate properly so it can harm the engine.
Overfilling your engine oil slightly such as in half a quart or less is not always a problem.
But overfilling the engine oil too much is bad and can cause engine failure so you must drain any excess engine oil to prevent engine failure which is a costly repair.