In the following year and a half, the tanker made eleven similar voyages carrying fuel oil to American ships in such scattered points as Devonport, England; Brest, France; the Panama Canal Zone; Ponta Delgada in the Azores; Glasgow, Scotland; and Newfoundland.

Hisko took on oil at New York for most of this period, although she did make three trips to the Gulf of Mexico to load fuel at Port Arthur, Texas, and Baton Rouge, Louisiana.

Several ships in her convoys, including a French cruiser, were torpedoed by German U-boats, but Hisko escaped unscathed with her valuable cargo.

On the night of 5–6 September 1918 in high seas and fog, Hisko was in collision with the 3,121-Gross register ton United Fruit Company passenger-cargo ship SS Almirante south of the Brigantine Shoals at approximately 39°21′N 74°13′W / 39.350°N 74.217°W / 39.350; -74.217 (Amirante), some 16 nautical miles (30 kilometres) off the coast of New Jersey near Atlantic City.

Despite substantial damage to her bow, Hisko was able to continue to New York, but Almirante sank quickly in some 70 feet (21 meters) of water.