Marias completed her shakedown cruise in Chesapeake Bay 8 March and ten days later was underway to Aruba, Netherlands West Indies.

On 20 August she proceeded from Eniwetok in convoy to Manus, to refuel ships moving against the Japanese in the Philippines, Volcano, Bonin, and Palau Islands.

In mid October, she began to operate in support of the U.S. 3rd Fleet, providing the fuel for their strikes on the Visayan Islands and the ensuing Battle for Leyte Gulf.

Two weeks later, as the campaign in the Philippines moved north, Marias loaded her tanks and sailed for those islands to fuel the ships conducting strikes on Luzon.

Following the signing of the surrender terms, Marias entered Tokyo Bay, remaining there, with the exception of a voyage to Ulithi for fuel, until departing for the United States 27 October 1945.

Marias arrived San Pedro, California, 10 November, underwent yard overhaul and departed again for the western Pacific 5 February 1946.

For the next four years, with one interruption - a cruise to Bahrein, 27 July to 9 October 1950 - the ship delivered fuel from the U.S. West Coast to Pearl Harbor and Alaskan ports.

On 9 May 1955, she was assigned indefinitely to the Mediterranean, home ported at Barcelona, Spain, and for the ensuing years operated as part of Service Force, 6th Fleet.

Her 1962 deployment was followed by a Caribbean cruise to support the ships enforcing the quarantine policy during the Cuban Missile Crisis of October to November of that year.