1998 Buick Riviera Owner's Manual - Page 248

If you get gasoline on yourself then and something ignites you could be badly it, 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 stop. Then unscrew to the cap all way. the Be careful not to spill gasoline. Clean gasoline from painted surfaces as soon possible. See "Cleaning the as Outside of Your Vehicle" in the Index. When you put the cap back on, it to the right turn (clockwise) until you hear a clicking sound. Make sure you fully install the cap. diagnostic system The can determineif the fuel cap has been leftoff or improperly installed. This would allow to evaporate fuel into the atmosphere. See "Malfunction IndicatorLamp'' in the Index. NOTICE: If you needa new cap, be sure to get theright type. Your dealer can get one you. If you get for the wrong type,it may notfit properly. This may cause your malfunction indicator lamp to light and your fueltank and emissions system may be damaged. See "MalfunctionIndicator Lamp" in the Index. 6-7