The technician listens to the customer’s complaints and asks the right questions. Then he prepares the car for a road test. While doing this, he checks the oil level and finds it to be low. This somewhat verifies that the engine is using excessive amounts of oil, so he removes the spark plugs from the engine to check for signs of oil burning. The spark plugs are clean and show no signs of oil. The technician then checks the engine for leaks hoping to find the cause of the excessive oil loss. The only wet spot is to the rear of the oil pan and the front of the bell housing. A leaking rear main seal is the likely cause of the oil loss. However, this does not explain the other problems of poor fuel mileage and a general lack of power. If the engine had been burning oil, all of the problems could have been related.