Buick 2001 Park Avenue Owner's Manual page 270

While refueling, hang the tethered cap from the hook on
the fuel 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.
CAUTION:
If you get gasoline on yourself and then
something ignites it, you could be badly burned.
Gasoline 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 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
(clockwise) until you hear a clicking sound. Make sure
you fully install the cap. 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" in
the Index.
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