1998 Pontiac Bonneville Owner's Manual - Page 258

To remove thecap, turn it slowly to the left (counterclockwise). The cap has a spring it; if you let in go of the cap too soon, it will spring backto the right. When you putthe 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 off can determine ifthe fuel cap has been left or improperly installed. This would allow to fuel evaporate intothe atmosphere. See "Malfunction Indicator Lamp"in the Index. If you get gasoline on yourself then and something ignites it, you could be badly burned. Gasoline canspray out on you if you open the fuel fillercap too quickly.This spray can happen if your tank is nearly full, and is more likely in hot weather. Open the fuel fillercap slowly and wait for any "hiss" noise stop. Then unscrew to the cap allthe way. NOTICE: If you need a new cap, be to getthe right sure type. Yourdealer can get one you. If you get for the wrong type,it may not fit properly. This may cause your malfunction indicator lamp to light and your fueltank andemissions system may be damaged. See "MalfunctionIndicator Lamp" in the Index. 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. 6-7