1994 Chevrolet Astro Owner's Manual - Page 221

NOTICE: If you try to do your own service work without knowing enough about it, your vehicle could be damaged. The 8th digit of your Vehicle Identification Number (VTN) shows thecode 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 87 octane or higher. With the at 4.3L (Code W) engine, use premium unleaded gasoline rated at9 1 octane or higher for high power performance, when towing trailer or with a high a payload requirement. But when operating with light load as a normal a condition, you may use middle grade or regular unleadedgasolines. The gasoline you use should meetspecifications ASTM D4814 in the U.S. and CGSB 3.5-92 in Canada. These fuels should have the proper additives, so you should not haveto 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 the pump. And only on unleaded nozzles will fit into your vehicle's filler neck. Be sure the posted octaneis atleast 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 youdrive. 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 hear a little you pinging noise when you're accelerating driving up ahill. That's normal, or and you don't have to buy a higher octane fuel to get rid of it. It's the heavy, constant knock that means have a problem. you 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. 6-3