My oils very thin and black when i change it , the car smokes black a little sometimes.Is this normal or is it from low oil pressure?

Probably a worn out engine or oil pump. Do you always change the oil and filter every 3 months or 3,000 miles?

you could pull valve covers and make sure return holes are not gunked up. or it could be like mod said.

My experience with low oil pressure is that the oil pumps rarely wear out and are not able to deliver their rated capacity...In high mileage engines, this situation usually happens because of worn main bearings and connecting rod bearings let the oil run out too fast and the pump just can't keep the hot oil flowing with enough capacity to prevent the oil pressure from going low.....your bearings should not be that worn especially considering the relatvely low mileage you have on your engine (unless it has been abused..ie ran low on oil, filter not changed for an extended time,... anything to starve the bearings of oil or feed them dirty, unfiltered oil) You should try a straight weight oil (SAE 40 or 50) to see if that helps...The only other thing is that your oil pickup screen may be partially plugged...no one has put a foreign substance in your motor like sugar or something....have they?

The oil pickup tube screne on the oil pump is small. I would suspect the the engine is sluged and the pump is starving for oil. Remove the oil pan to see. If clean sounds like a worn engine.