Pakistan State Oil Company Limited , namely PSO was found in 1976, as a result of an amalgamation of the formal three oil marketing companies i.e. : Pakistan National Oils Limited, Premiere Oil Company and Esso Undertakings in Pakistan.

As the largest Oil Marketing Company in Pakistan, Pakistan State Oil is committed to efficiently meeting the country's energy needs beyond the 20th Century. Further, PSO has been listed in Asia's largest 1000 companies by Asia Week.

Hubco relations with PSO are governed by Fuel Supply Agreement (FSA) under which Hubco purchases all its RFO requirements from PSO. RFO is devlivered via 78km long pipeline which is built exclusively for Hubco.