I offer this check list to anyone initially questioning their mileage:

Check the back/trunk. Are you carrying weight that isn't really necessary? (I state this because my wife loaded the trunk of my HCH with diet Coke when it was on sale. 16 twelve packs equaled about 128 pounds of extra weight.)

Check the air pressure of the tires. Whether you subscribe to increasing the air pressure or not, having mismatched pressures is one thing most people agree can tank your mileage. The front tires should be equal and the back tires equal. They should be in the generally recommended pressure set by the manufacturer of the car.

Lastly, check to make sure that there are no obstructions to the engine air intake ductwork. Sometimes, debris can fly into the grill and block this intake.

Remember that you are still "breaking in" your car. Most people see a bump in mileage at the 3-5k mile mark.

Good luck.

-Charlie...