1995 GMC Sonoma Owner's Manual - Page 221

knocking noise when you drive. If it's bad enough, it can damage your engine. If you're using fuel rated at 91 octane or higher and you still hear heavy knocking, your engineneeds service. But don't worry if you hear a little pinging noise when you're accelerating or driving a hill. That's normal, up and you don't have to buy a higher octane fuel to get rid of it. It's the heavy, constant knock that means you have a problem. What about gasolinewith blending materials that contain oxygen (oxygenates), such as MTBE or alcohol? MTBE is "methyl tertiary-butyl ether." Fuel that is no more than 15% MTBE is fine for your vehicle. Ethanol is ethyl or grain alcohol. Properly-blended fuel that is no more than 10% ethanol is fine for your vehicle. Metlznnol is methyl or wood alcohol. NOTICE: Fuel that is more than methanol is bad for your vehicle. 5% Don't useit. It can corrode metal parts in your fuel system and also damage plastic and rubber parts. That damage wouldn't be covered under your warranty. And even 5% or less, there at must be "coso1vents" and corrosion preventers in this fuel to help avoid these problems. Gasolines for Cleaner Air Your use of gasoline with deposit control additives will help prevent deposits from formingin 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. In addition, some gasoline suppliers are now producing reformulated gasolines. These gasolines are specially designed to reduce vehicle emissions. General Motors recommends you use reformulated gasoline. that 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. 6-3