I have a car and I've got a car both mean... I have a car! I've got a car is considered a little more informal, by some. I have a cold... atishoo! I've got a cold... atishoo! No difference in meaning. 'I got a car' is incorrect as it stands. However, it would be correct if you add to it like this... "I got a car yesterday" ... as in I bought a car yesterday. When people speak you may HEAR "I got a car" but that's because the ..'ve ...almost disappears. You don't hear it, but it's there. (Or it SHOULD be!) Actually, when I'm being REAL informal I might say "I got a car, yeh," but I am being very sloppy.

The first two are equivalent and indicate possession of a car. The third one would most likely be interpreted as "I obtained a car," although colloquially it can also mean I possess a car.

Well, in the English writing, it is better to use to formal one which is ''I have a car." Even though 'I have got a car' can deliver the same meaning, it is usually used in the British English and it is informal. You may use that when speaking English, but it is better to use "I have a car" when writing.