A quick background of my car:
I bought a used 2007 WRX (not STI) with 36k miles on it in April, but didn't drive it until mid May due to school(left at home). I had the clutch go out on me towards the end of June. I had only put ~500 miles on it so with the extended warranty we had it replaced for free. As of now the clutch has about 2.5k miles, other than that everything else is original and stock(that I know of) with no mods on it. The mileage is a little over 39k.
My problem is now that I used to get about 18-20 MPG city. Now, however I'm getting around 14. I don't know the exact math, but I've driven 140 miles in almost 3/4 a tank, so I'd say I'm getting around 13-15 MPG city. Anyone know a reason for a sudden drop in gas mileage? I do need my oil changed soon, but would that cause a huge drop in gas mileage.