Two mornings ago, i started my car and had to go run back in the house to get something. When i came out my front door i noticed a oil spot. Since then i drove my beater minivan and have checked for oil on the outside of the motor twice now. I see no large leaks! I have yet to notice any oil under it after that day. No leaks from simple places like the oil filter or dipstick or even the oil pan gasket. What are some common places for oil leaks? My biggest fear is a main seal or something. BTW i am running mobil one for the first time.