My car is a 2004 STi. I just bought this car at 70,000 miles. All my driving is in town and I don't drive the car hard or brake quickly. The last two tanks averaged ~13mpg. I was shocked, so I checked my tire pressure. The front wheels were 10psi under the reccomended 36 and the rear tires were at 19psi rather than the reccomended 30. I'm wondering if this could be the cause of the mileage drop or if it could be something else. I just changed the oil and got new spark plugs the day I purchased it, so those aren't the cause.