Petró-Chico was a branch of Poseidon Oil operating in the barren Mexican oil fields following the American take-over in the early 2050s. Based in the states of Veracruz, Puebla, and Hidalgo, Petró-Chico oil flowed across the Rio Grande into the southern US, as far as Las Vegas, Nevada. Bearing the ominous label of "un amigo de Poseidon Energy", it is meant to showcase Poseidon's far-reaching and international hold over the world's economy.
- The slogan translates to "A friend of Poseidon Energy".
- Various signs and former gas stations of the company can be seen in-game.
- Petró-Chico translates to "Oil-Boy" in Spanish.
Petró-Chico appears only in Fallout: New Vegas.