GMC Sonoma 2001 Owner's Manual page 274

While refueling, hang the cap by the tether from
the hook on the fuel filler door.
To remove the cap, turn it slowly to the
left (counterclockwise). The cap has a spring
in it; if you let go of the cap too soon, it will spring
back to the right.
6-8
CAUTION:
If you get fuel on yourself and then something
ignites it, you could be badly burned. Fuel can
spray out on you if you open the fuel filler cap
too quickly. This spray can happen if your tank
is nearly full, and is more likely in hot weather.
Open the fuel filler cap slowly and wait for any
"hiss" noise to stop. Then unscrew the cap all
the way.
Be careful not to spill fuel. Clean fuel from painted
surfaces as soon as possible. See "Cleaning the Outside
of Your Vehicle" in the Index.