1994 Chevrolet Blazer Owner's Manual - Page 239

Fuel 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 the Index.) Use regular unleaded gasoline rated at 87 octane or higher. With the 4.3L (Code W) engine, use premium unleaded gasoline rated at 91 octane or higher for high power performance, when towinga trailer or with a high payload requirement. But when operating with a light load as a normal condition, you may use middlegrade or regular unleaded gasolines. The gasoline you use should meet specifications ASTM D48 14 in theU.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 the posted octane is at least9 1 for premium, 89 for middle grade and 87 for regular. 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 91 octane or higher 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 it. It's the heavy, constant knock that means you have a problem. What about gasoline with blending materials thatcontain oxygen (oxygenates), such as MTBEor 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 for your vehicle. Methanol is methyl or wood alcohol. NOTICE: Fuel that is more than5% methanol is bad for your vehicle. 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. 6-3