What is going on with my gas mileage?

Good question, are you paying attention.  I recommend checking it with some frequency and see it there is an unexplained drop in your MPGs.  An explained change could be using your AC more, more in town driving hauling around extra people or a load of stuff in the trunk, like that.  Unexplained (and by unexplained I really mean undiagnosed because there is always an explanation , you just don’t have the explanation yet) drops could mean a number of things from under inflated tires, stuck or leaky injectors, brakes hanging up, etc.  If you have the ability to check those things, get on it!  If not, sounds like an opportunity to visit your trusty mechanic.  Do the math, save those Washington’s!  Its easy, fill up the tank, reset the tripometer, drive, refill, divide the miles by the gallons used.