1994 GMC Jimmy Owner's Manual - Page 239

The 8th digit of your Vehicle Identification Number (VIN) shows the code letter for your engine.You will find the VIN at the top of your left instrument panel. (See "Vehicle Identification Number" the Index.) in Use regular unleaded gasoline rated at 87 octane or higher. With the 4.3L (Code W) engine, use premium unleaded gasoline rated at octane or 91 higher for high power performance, when towing a trailer or with a high payload requirement. But when operating with a light load as a normal condition, you may middle grade or regular unleaded gasolines. use The gasoline you use 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 addanything to the fuel. the In theU.S. and Canada, it's easy tobe sure you get right kindof gasoline (unleaded). You'll "UNLEADED" right on the pump. And only see unleaded nozzles will into your vehicle's filler neck. fit Be sure the posted octane is at least 91 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 higherand you still hear heavy knocking, your engine needs service.But don't worry if you hear a little pinging noise whenyou're accelerating or driving a hill. That's normal, up and you don't have to buy a higher octane fuel to get rid it. It's the heavy, of you constant knock that means have a problem. What about gasoline withblending 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 thatis no more than 10% ethanol is fine for your vehicle. Methanol is methyl or wood alcohol. NOTICE: Fuel thatis 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