American Petroleum Institute (API)

The American Petroleum Institute (API) developed a recommended uniform marking system. A color-code and symbol system to indicate the different grades of gasoline and fuel oils is used by bulk liquid petroleum marketing and storage facilities. These markings are typically found at loading racks, transfer valves, and connections. This system also classifies the many hydrocarbon fuels and blends into leaded and unleaded gasoline, gasoline additives, distillates, and fuel oils.

Image of a American Petroleum Institute color codes, a dark blue border with a dark blue band at the top, displaying white text stating “A.P.I. Color Code.” Below that multiple lines of black text with three images to the left. The top is a white circle with a black outline and a black plus symbol inside with the text unleaded regular. The next line is a blue circle with a white plus sign and the text unleaded midgrade. The next line is a red circle with a white plus sign and the text unleaded premium. Below that a black circle with a black plus sign and the text Unleaded Regular W/EXT. Underneath that a blue circle with white plus sign and the text Unleaded Midgrade W/EXT. Underneath a red circle with a white plus sign and the text Unleaded Prem. W/EXT. Underneath a brown hexagon with the text Kerosene. Next is an orange circle with Vapor Recovery. Underneath a black hexagon with a horizontal yellow stripe and #1 Fuel Oil. Next is a green hexagon with #2 Fuel Oil. Underneath that is a yellow hexagon with the text Diesel, Low Sulfur. The bottom line is a yellow hexagon with a black horizontal stripe with the words Diesel, High Sulfur.