1995 GMC Yukon Owner's Manual - Page 285

Be sure the posted octane is a t least 87. I f the octane is less than 87, you may get a heavy knocking noise when you drive. I f it's bad enough, it can damage your engine. If you're using fuel rated at 87 octane or higher and you still hear heavy knocking, your engineneeds service. But don't worry if you hear a little up pinging noise when you're accelerating or driving a hill. That's normal and you don't have to buy a higher octane fuel t o get rid of pinging. 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 for your vehicle. Ethcrrlol is ethyl or grain alcohol. Properly-blended fuel that is no more than 1 Oc/c ethcrrwl is fine for your vehicle. Metlzcrr1ol is methyl or wood alcohol. NOTICE: Fuel that is more than5% methanol is bad for your vehicle. Don't use it. It corrode metal parts in your fuel system and can also damage plastic and rubber parts. That damage wouldn't be 5% covered under your warranty. And even at or less, there must be "cosolvents" and corrosion preventers this fuel to in help avoid these problems. Gasolines for Cleaner Air Your use of gasoline with deposit control additives will help prevent deposits from forming i n 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 ail-. especially in those parts of the country that have high carbon monoxide levels. In addition, some gasoline suppliersare now producing reformulated gasolines. These gasolinesare 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. 6-3