Hi my mother has a 2000 mb c230 with 70000 miles and its having some problems. Yesterday it didn't really have much oil in it so she put in a quart and she pretty much drove all day with it. This morning I tried to start the car and the engine knocks really hard and then shuts off as soon as I take my foot off the gas. I checked the oil and there was no oil in the car. So I put 3 quarts in and it still has the same problem. There wasnt any leakage while I was running the engine with oil in it. Does anyone know what seems to be broken? thank you