1994 GMC Suburban Owner's Manual - Page 250

Maintenance Schedule Section 7 of this manual, "Scheduled Maintenance Services", explainsthe maintenance your new vehicle needs, and when it should be done. It also has a form thatyou can use to record the maintenance work done on your vehicle. Be sure to read this information. Fuel (Gasoline Engine] If your vehicle has a diesel engine, see"Diesel Fuel Requirements and Fuel System" in this Section. For vehicles with gasoline engines, please read this. Use regular unleaded gasoline rated at 87 octane orhigher. It should meet specifications ASTM D4814 in the U.S. 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 U.S. 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 theposted octane is at least 87. If the octane is less than 87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine. If you're using fuel rated at 87 octane orhigher and you still hear heavy knocking, your engine needs service. But don't worry if you hear a little 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 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 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 thatis more than5% methanol is bad for your vehicle. 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 C4coso1vents" and corrosion preventers in this to fuel help avoid these problems. 6-4