1995 GMC Safari Owner's Manual - Page 209

In the United States and Canada, it's easy to be sure you get the right kind of gasoline (unleaded). You'll see UNLEADED right on the pump. And only unleaded nozzles will fit into your vehicle's filler neck. Be sure the posted octane is at least 91 for premium, 89 for middle grade and 87 for regular. If the octane is lessthan 87, you may get a heavy knocking noise when youdrive. If it's bad enough, it can damage your engine. If you're using fuel rated at 91 octane or higher and youstill hear heavy knocking, your engine needs service. But don't worry if you hear little a pinging noise when you're accelerating or driving up a hill. That's normal, 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 gasoline with 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 foryour vehicle. Ethanol is ethyl or grain alcohol. Properly-blended fuel that is no more than 10% ethanol is fine foryour vehicle. Methanol is methyl or wood alcohol. NOTICE: Fuel that is more than methanol is bad for your vehicle. 5% Don't use it. 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 "cosolvents" 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 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 bedoing your part for cleaner air. Many gasolines are now blended with oxygenates. General Motors recommends that you usegasolines with these blendingmaterials, 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 that you usereformulated gasoline. 6-3