I just purchased a pre-owned 2008 Tribeca and am having trouble figuring out how to tell if there is gasoline in the car. The car has the curved line gas gauge icon on the dashboard but it never changes. I thought it would get smaller, or lower, as the gas was used, but it does not move. I have no idea how much gas is in the tank. The car has all kinds of computerized mechanisms to find out how much consumption per mile, etc. but not a quick glance as you are driving gauge. Is it broken or is that the way it is made to be? Thank you.