Combination ore-bulk-oil carriers and permanently moored floating storage units are two other variations on the standard oil tanker design.

By 1962 Malmfart had three vessels, of which two were ore-bulk-oil carrier, which allowed them to transport petroleum on the return voyage to Norway.

A fleet of smaller, "river-sized" (several thousand tonnes) ore-bulk-oil carriers have also been used for some decades on European Russia's waterways, primarily by Volgotanker.

An ore-bulk-oil carrier, also known as combination carrier or OBO, is a ship designed to be capable of carrying wet or dry bulk cargoes.

Derbyshire, an ore-bulk-oil carrier which disappeared in 1980 Mearns also led the 2001 expedition to the ship that sank Hood, the German battleship Bismarck, which had been found by Robert Ballard and his team in 1989.

Russia's Volgotanker Company, which owned a fleet of suitably sized petroleum tankers and ore-bulk-oil carriers, pioneered this route starting in August 1970, when Nefterudovoz-3 delivered a cargo of fuel oil to the White Sea port of Kandalaksha.