I recently bought a 2002 C230 Coupe with 33,000 miles on it. I know the seller, and she gave me a receipt for the service she had done at 30,000 miles (which included an oil change). I was driving this weekend (car now has about 33,700 miles) and the check engine oil level warning came on. I checked it and it was 2 quarts low!! Plus the oil on the dip stick looked a lot older than 3,700 miles (but I am no expert). 2 quarts low seems like a lot to me. Is this normal, or should I take it in to the dealer?