GMC Yukon 2007 Owner's Manual page 458

To open the fuel door, push the rearward center
edge inboard and release. The door will pop open.
To remove the fuel cap, turn it slowly
counterclockwise. The fuel cap has a spring in it;
if the cap is released too soon, it will spring
back to the right.
While refueling, hang the tethered fuel cap from
the hook on the fuel door.
458
CAUTION:
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If you spill fuel and then something
ignites it, you could be badly burned. Fuel
can spray out on you if you open the fuel
cap too quickly. This spray can happen if
your tank is nearly full, and is more likely
in hot weather. Open the fuel cap slowly
and wait for any hiss noise to stop. Then
unscrew the cap all the way.
Be careful not to spill fuel. Do not top off or overfill
the tank and wait a few seconds after you have
finished pumping before removing the nozzle.
Clean fuel from painted surfaces as soon as
possible. See Washing Your Vehicle on page 559.
When replacing the fuel cap, turn it clockwise until it
clicks. Make sure the cap is fully installed. The
diagnostic system can determine if the fuel cap has
been left off or improperly installed. This would
allow fuel to evaporate into the atmosphere. See
Malfunction Indicator Lamp on page 254.