2008 Chevrolet HHR Owner's Manual - Page 177

Here are four things that some owners ask about. None of these show a problem with your fuel gage: Boost Gage • At the service station, the gas pump shuts off before the gage reads full. • It takes a little more or less fuel to fill up than the gage indicated. For example, the gage may have indicated the tank was half full, but it actually took a little more or less than half the tank's capacity to fill the tank. • The gage moves a little when you turn a corner or speed up. • The gage doesn't go back to empty when you turn off the ignition. For your fuel tank capacity, see Capacities and Specifications on page 5-125. United States Canada If equipped, this gage indicates vacuum during light to moderate throttle and boost under heavier throttle. This gage displays the air pressure level in the intake manifold before it enters the engine's combustion chamber. This gage is automatically centered at zero every time the engine is started. Actual vacuum or boost is displayed from this zero point. Changes in ambient pressure, such as driving in mountains and changing weather, will slightly change the zero reading. 3-45