Unocal’s 76 Racing Gasoline offers two different types of racing gas: 108-octane leaded and 100-octane unleaded. The 100-octane unleaded is oxygenated and therefore legal for use in street-driven vehicles. Often, 100 may be more octane than you really need for your engine. You can mix the 100-unleaded with 92-octane pump gas to create the octane you need to eliminate detonation. Wusz also mentioned that unleaded can be mixed with leaded race gas. When you do this, the final octane number will be slightly higher than indicated in this chart, as small amounts of lead will increase the blended octane number. This chart is courtesy of 76 Racing Gasoline.