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Petro is a fuel in use by the Cylons.
Megan's children continually attack and destroy the petro dumps on Attila, forcing Specter to relocate the dumps inside Megan's castle, which is now the Cylon base of operations on the planet. These continual attacks force Specter to order additional supplies, notably petrol, laser pumps, laser rifles and metron bombs, which does not go unnoticed by Lucifer, Baltar's second in command (TOS: "The Young Lords").
- The name, derived from "petroleum", indicates that petro is some type of refined oil.