1995 Buick Riviera Owner's Manual - Page 213

Gasolines for Cleaner Air Your use of gasoline with deposit control additives will help prevent deposits from forming in your engine and fuel system. That helps keep your engine in tune and your emission control system working properly. It's good for your vehicle, and you'll be doing your part for cleaner air. Many gasolines are now blended with oxygenates. General Motors recommends that you use gasolines with these blending materials, such as MTBE and ethanol. By doing so, you can help clean the air, especially in those parts of the country that have high carbon monoxide levels. Fuel 3800 Supercharged L67 (Code 1) Engine The 8th digit of your vehicle identification number (VIN) shows the code letter for your engine. You will find the VIN at the top left of your instrument panel. (See "Vehicle Identification Number" in theIndex.) Use premium unleaded gasoline rated at 91 octane or higher for best performance. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well. The gasoline you use should meet specifications ASTM D4814 in the United States and CGSB 3.5-92 in Canada. These fuels should have the proper additives, so you should not have to add anything to the fuel. In the United States and Canada, it's easy to be sure you get theright kind of gasoline (unleaded). You'll see UNLEADED right on the pump. And only unleaded nozzles will fit intoyour vehicle's filler neck. Be sure the posted octane for prernium at least 91 (at is least 89for middle grade and for regular).If the octane 87 is less than 87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine. In addition, some gasoline suppliers are now producing reformulated gasolines. These gasolines are specially designed to reduce vehicle emissions. General Motors recommends that you use reformulated gasoline. By doing so, you can help clean the air, especially in those parts of the country that have high ozone levels. You should ask your service station operators if their gasolines contain deposit control additives and oxygenates, and if they have been reformulated to reduce vehicle emissions. If you're using fuel rated at 91octane or higher and you still hear heavy knocking, your engine needs service.