Suddenly, 4 days ago, my MPG dropped from 23 MPG to 18 MPG, during my routine 90 mile roundtrip commute to work. Then the engine warning light came on. I took the car to the dealer and they said the Air Cooler Temperature Sensor failed and needed to be replaced. It will be flown in from Memphis TN. What this has to do with MPG, and whether this solves the problem, remains to be seen. I have 7200 miles on the car already and will have them change the oil anyways, despite what the manual says (Dealer recommended it also). Will report on the fix, hopefully this week.