Chevrolet 2008 Optra Owner's Manual page 211

To remove the fuel cap, turn it slowly to the left
(counterclockwise). The fuel cap has a spring in it; if the
cap is released too soon, it will spring back to the right.
CAUTION:
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Fuel can spray out on you if you open the fuel
cap too quickly. If you spill fuel and then
something ignites it, you could be badly burned.
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 5-82.
When replacing the fuel cap, turn it to the right
(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 3-34.
CAUTION:
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If a fire starts while you are refueling, do not
remove the nozzle. Shut off the flow of fuel by
shutting off the pump or by notifying the
station attendant. Leave the area immediately.
Notice: If you need a new fuel cap, be sure to get
the right type. Your dealer/retailer can get one
for you. If you get the wrong type, it may not fit
properly. This may cause your malfunction indicator
lamp to light and may damage your fuel tank and
emissions system. See Malfunction Indicator Lamp
on page 3-34.
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