[1] For surface running, the boats were powered by two 600-brake-horsepower (447 kW) diesel engines, each driving one propeller shaft.

After exercises along the West Coast, L-6 departed Pacific waters on 20 April 1918, arriving Charleston, South Carolina, on 10 June.

Following a brief overhaul, the submarine patrolled off Charleston until she sailed on 15 October for the eastern Atlantic.

After making stops in Caribbean Sea and Central American ports, L-6 arrived San Pedro, California, on 14 February 1919, completing one of the best long-distance seagoing performances of the United States's youthful submarine force.

Upon arrival Hampton Roads, L-6 decommissioned on 25 November 1922, and was sold to M. Samuel and Sons on 21 December 1925 for scrapping.