Retailers base their grades of gasoline at the pump based on the octane levels. As EIA explains, the lowest octane level (usually 87) is considered regular, 89-90 is midgrade, and premium has the ...

The Texas Department of Agriculture is investigating 16 Houston-area gas stations for allegedly mixing lower-octane gasoline with higher-octane, higher-priced gas. The state launched its ...

Most states have the option of choosing octane ratings of 87 (regular), 88–90 (midgrade) and 91–94 (premium). But in a few states, the gas pumps look a little different.