Oldsmobile 1998 Aurora Owner's Manual page 142

Turn on the system by pressing any button except
RESET, ENTER or OFF. When you turn on the ignition,
the DIC will be in the mode last displayed when the
engine was turned off. Keep in mind that this also
applies to the OFF mode.
To turn off messages on the DIC (except LOW OIL
PRESSURE, LOW BRAKE FLUID, PARK BRAKE
SET and the hot engine warnings), press any button
on the DIC.
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You will need to open the cover to access the control
buttons. To open the cover, push the button located to
the right of the cover.
To close the cover, push it down to its closed position.
Fuel Economy
The ECON button displays average fuel economy and
instantaneous fuel economy calculated for your specific
driving conditions.
Press ECON to display average fuel economy, such as:
25.2 AVG MI/GAL or 9.3 AVG WlOO KM
Press ECON again to display instantaneous fuel
economy, such as:
28 INST MUGAL or 8.4 INST W l O O KM
Press again to return to average fuel economy.
The average fuel economy is viewed as a long-term
approximation of your overall driving conditions.
If you press RESET in this mode while you're driving,
the system will begin figuring fuel economy from that
point in time.