1996 Chevrolet Corvette Owner's Manual - Page 234

Fuel If you have the 5.7L Code engine, use premium 5 unleaded gasoline rated at octane or higher. 91 If you have the 5.7L Code engine, use premium P unleaded gasoline rated at octane or higher for best 91 performance. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well. At a minimum, the gasoline you should meet use specifications ASTM D4814 in the United States and CGSB 3.5-M93 in Canada. Improved gasoline specifications have been developed by American the Automobile Manufacturers Association(AAMA) for better vehicle performance and engine protection. Gasolines meeting the AAMA specification could provide improved driveability and emission control system protection compared other gasolines. to Be sure the posted octane premium is atleast 91 for (at least 89 for middle grade and87 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 candamage your engine. If you're using fuel rated at the recommendedoctane or higher and you still hear heavy knocking, your engine needs service. But don't worry if youhear a little pinging noise whenyou're accelerating or driving up a hill. That's normal, and you don't haveto buy a higher octane fuel to get rid of pinging, It's the heavy,constant knock that means you have a problem. If your vehicle is certified to meetCalifornia Emission Standards (indicated on the underhood tune-up label), it is designed to operate on fuels that meet California specifications. If such fuels are not available in states adopting California emissions standards, your vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn on and/or your vehicle may fail a smog-check test. If this occurs, return to your authorized Corvette dealer for diagnosis to determine the cause of failure. In the event it is determined that the cause of the condition is the type offuels used, repairs may not be covered by your warranty. 6-3