GMC 1994 Yukon Owner's Manual page 259

While refueling, hang
the cap inside the fuel
door.
To take off the cap,
turn it slowly to the
left.
Be careful not to spill gasoline. Clean gasoline from painted surfaces as
soon as possible. See "Cleaning the Outside of Your Vehicle" in the Index.
When you put the cap back on, turn it to the right until you hear a clicking
noise.
I
NOTICE:
If you need a new cap, be sure to get the right type. Your dealer
can get one for you. If you get the wrong type, it may not fit or
have proper venting, and your fuel tank and emissions system
might be damaged.
6-13