For the first time in nearly eight decades, the ubiquitous Pemex gas stations have competition along Mexico's highways and city streets.

Two companies have opened three gas stations under their own brands, breaking one of the state-owned petroleum company's last monopolies. Opening the retail sector to competition was part of energy reforms passed in 2014.

Mexico's Hid Rosina opened a re-branded Pemex gas station as its own this week in Mexico City and Mexican company La Gas opened two stations in Campeche and Merida. Both will be selling Pemex gasoline.

U.S.-based Gulf Oil announced it would open its first four gas stations in Mexico between June and July.