All the Chevrolet V-8 engines produced by General Motors have minimum octane requirements to prevent the audible knocking sound, sometimes called "spark knock," that often occurs with low-octane gasoline. A small amount of knocking won't damage the engine but heavy knocking typically caused by using a gasoline with a lower octane rating than required can cause engine damage and leave you with a costly repair bill. Knowing when to use super unleaded gasoline in a Chevy V-8 engine requires knowing and following a few simple rules.
Use regular unleaded gasoline with an octane rating of 87 on all Chevrolet V-8 engines except the 6.2-liter; for that engine, use super unleaded gasoline with an octane rating of 91. You can use this higher-octane gasoline in all of the V-8s; however, it is overkill and you'll pay more without realizing any benefit.
You can use a lower-octane gasoline at high altitudes. If you're traveling through the mountains, for example, you may see octane ratings lower than 87 on gas pumps. In this case, refer to the descriptive adjectives: for example, use "Regular" for the V-8s except the 6.2-liter engine and use "Super," "Premium" or "Extra" for that engine. Fill up with higher-octane gasoline when you descend to lower altitudes.
Increase the octane rating any time you hear heavy knocking. For example, in a pinch, you could use a lower-octane fuel than recommended (but not significantly lower). If 91-octane gasoline is not available, you could use 87-octane in the 6.2-liter, but not on a regular basis if knocking becomes pronounced.
