at port. The auxiliary generator, six-cylinder Wärtsilä 6L26A, has an output of . While underway at , the fuel consumption of the ship's main engines is 56 tons of heavy fuel oil per day when loaded and 40 tons per day in ballast. Her tanks can store of heavy fuel oil for the main engines, of diesel oil for the auxiliary generator, steam boilers and inert gas system, and of lubrication oil. When built, Mastera and her sister ship were the first tankers propelled by ABB Azipod electric azimuth thrusters capable of rotating 360 degrees around the vertical axis. The pulling-type VI2500 pods in these two ships, with a nominal output of 16 MW and fixed-pitch propellers turning at 86 rpm, are the most powerful ice-strengthened Azipod units ABB has ever produced. The forward-facing propeller increases the propulsion efficiency due to optimal water flow to the propeller and thus improves fuel efficiency. In addition an azimuthing thruster's ability to direct thrust to any direction also results in excellent manoeuvrability characteristics that exceeds those of ships utilizing traditional mechanical shaftlines and rudders. The turning circle of the Azipod-equipped double acting ships is only half a kilometer at full speed, half of that of a traditional oil tanker of the same size. This is a significant safety factor as the stopping distance of a traditional tanker can be up to . For maneuvering at low speeds in harbours, the ship is also equipped with two 1,750kW bow thrusters. Icebreaking capability The icebreaking capability of the double acting tankers proved to be superior to other ships since the beginning — in shuttle service between Primorsk, Russia, and the Finnish refineries the tankers require no icebreaker assistance and have even acted as an icebreaker for other merchant ships that have utilized the wide channel opened by the Aframax tanker. However, this has not been intentional — when the world's largest 1A Super class ice tanker Stena Arctica, also owned by Neste Shipping, became stuck in ice outside the port of Primorsk during the winter of 2009–2010, a decision was made to leave the assisting to Russian icebreakers. The ships have performed beyond expectations in both level ice up to thick, which can be broken in continuous motion at , and ridges up to deep, which can be penetrated by either allowing the forward-facing propeller to mill (crush) the ice or breaking the ridge apart