Shipped
The window sticker gives one MPG figure. Your commute, tires and driving give another.
Log each fill-up with the odometer reading, the gallons, the price and the trip meter reading. Gimme a View works out the MPG and the cost of each tank. Without a trip meter reading, it uses the miles since your last fill-up. After a few months you can see what the car costs to run, and spot MPG that starts to slip.