I drove the car on Saturday and it fine until we got closer to the house. The oil light came on and then it turned off and the car started running really funny. Then we hard a knocking sound in the engine. Once we got home we added a quart and a half of oil and let it run through the engine and the knocking sound got lower. Then we let the car sit all night and woke up the next checked the oil levels again and they were fine. We started the car to see if it was still knocking and when you press the accelerator it was knocking. What is wrong with my car and how much will it cost to get fixed?