1996 Mercury Grand Marquis Owner's Manual - Page 81

If you calculate your average fuel economy by dividing miles traveled by gallons used, your figure may be different than displayed because of: u Your vehicle not being perfectly level during fill-up u Differences in the automatic shut-off points on the fuel pumps at service stations fill-up to another u Variations in top-off procedure from one u Rounding of the displayed values to the INST ECON - Instantaneous Fuel Economy Select this function to calculate your instantaneous fuel economy. Your instantaneous fuel economy is the fuel economy you get at any particular moment. For example, you can see what your fuel economy is in heavy traffic or on an open highway. nearest 0.1 gallon (liters) on the fuel gauge. Your vehicle must be moving to calculate fuel economy. When your vehicle is not moving, instantaneous fuel economy is displayed at 0 miles per gallon or 99 liters per 100 kilometers. When you are moving, the display may read anything between 0 and 99 miles/gallon (1 to 99 L/km). Instantaneous fuel economy cannot be reset. 78