Have you had your vehicle a while and the mileage has dropped, or has it always been this low?
I would check the odo with a GPS if you have/can borrow one.
Also check to see if any brakes (including parking) are dragging.
Get your tires up to near max pressure, or as high as your spine will allow.
If you had an oil analysis done, you could see if you have some fuel dilution which may indicate a leaking injector (don't let 240Joe know you wasted money on an oil analysis though

).
Drive like there is an egg between your foot and the pedals!
Tim