GMC 2009 Yukon XL Owner's Manual page 238

Fuel Range
Press the trip/fuel button until FUEL RANGE displays.
This display shows the approximate number of
remaining miles (mi) or kilometers (km) the vehicle can
be driven without refueling. The display will show
LOW if the fuel level is low.
The fuel range estimate is based on an average of the
vehicle's fuel economy over recent driving history
and the amount of fuel remaining in the fuel tank.
This estimate will change if driving conditions change.
For example, if driving in traffic and making frequent
stops, this display may read one number, but if the
vehicle is driven on a freeway, the number may change
even though the same amount of fuel is in the fuel
tank. This is because different driving conditions produce
different fuel economies. Generally, freeway driving
produces better fuel economy than city driving.
Fuel range cannot be reset.
Average Economy
Press the trip/fuel button until AVG ECONOMY displays.
This display shows the approximate average miles
per gallon (mpg) or liters per 100 kilometers (L/100 km).
This number is calculated based on the number of
mpg (L/100 km) recorded since the last time this menu
item was reset. To reset AVG ECONOMY, press and
hold the set/reset button.
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Fuel Used
Press the trip/fuel button until FUEL USED displays.
This display shows the number of gallons (gal) or
liters (L) of fuel used since the last reset of this menu
item. To reset the fuel used information, press and hold
the set/reset button while FUEL USED is displayed.
Timer
Press the trip/fuel button until TIMER displays.
This display can be used as a timer.
To start the timer, press the set/reset button while
TIMER is displayed. The display will show the amount
of time that has passed since the timer was last
reset, not including time the ignition is off. Time will
continue to be counted as long as the ignition is
on, even if another display is being shown on the DIC.
The timer will record up to 99 hours, 59 minutes
and 59 seconds (99:59:59) after which the display will
return to zero.
To stop the timer, press the set/reset button briefly while
TIMER is displayed.
To reset the timer to zero, press and hold the set/reset
button while TIMER is displayed.