In addition, the steamer was equipped with eight throttle reversing steam winches for quick loading and unloading of cargo from shelter deck spaces.

[10] After loading a cargo of 81,000 barrels of oil the tanker left for San Francisco and reached her destination on March 12, successfully concluding her maiden voyage.

She also made occasional trips along the Pacific coast to ports such as Vancouver, Portland or Seattle, and on occasion took her cargo to Honolulu.

In addition, Montebello started making trips to Balboa in the Panama Canal area and Chilean ports of Antofagasta, Iquique and Taltal.

During the night of 5 October 1930 while the tanker was at the Los Angeles Shipbuilding Corp. undergoing repairs she was boarded by a lone bandit who after shooting the third mate in the head proceeded to rob the safe in the captain's cabin and crew lockers getting away with nearly $3,000 in cash without being seen by any other witnesses.

The police arrested a former Union Oil engine-room employee in connection with this robbery but he was later released due to lack of evidence against him.

[24] The tanker was under command of captain Olof Walfrid Eckstrom, had a crew of thirty-eight and carried a cargo of 75,346 barrels of crude oil bound for Vancouver.

The captain immediately ordered the ship full speed ahead and to assume a zigzag course and informed the Navy about submarine sighting.

[25][26] Fortunately for the crew the hold where the torpedo struck was dry and did not contain any oil; however, the resulting explosion blew away the deck house and the radio room and knocked down the forward mast.

[27][28] In an expedition conducted on November 7, 1996, the submersible Delta descended with two men on board to the wreck at a depth of 880 feet (270 m) and found Montebello sitting upright on the bottom.

While the bow was broken from the impact with the sea floor, the overall condition of the wreck was thought to be quite good, giving rise to the concern that she could still hold her liquid cargo.

[29] In August 2010 the wreck was examined by a robot submarine from the Monterey Bay Aquarium Research Institute[29] to determine whether the oil cargo was still on board and whether it posed a possible environmental threat.

[29] Further explorations of the wreck were scheduled for 2011 at an expected cost of $2.3 million, to be paid from a fund which oil companies pay into for such situations.