Premium gas is generally considered any type of gasoline with an octane level of 91 or greater, with 91 octane and 93 octane being the most common versions of premium gasoline available at gas stations in the United States. Therefore, premium gas has an octane level of 91 or higher. Regular gas, on the other hand, typically has an 87-octane rating, and the 88-90 range is considered midgrade.