Beginning World War II, the boiler remained filled with water, and in Winter the plant room was heated to keep the temperature above the freezing point (operationally for military purposes, 24 hours a day). Between the years 1941 and 1953 larger revisions were done: Boiler repairs, extension of the upper deck, and replacement of the sun awning by a solid roof. The coal firing was replaced by a heavy oil firing unit in 1951, allowing machine staff to be reduced (in her early years, Stadt Zürich had a crew of 8). The following general overhaul and rebuilt was done in spring 1956. Unfortunately, the Art Nouveau equipment of the salon also was dismantled and replaced by a simple wood veneer. During restorations of 1989/90 and 2003/04, the ship's interior was returned into its original appearance using historically sourced material, so that a similar room experience is given today. In 1960 and 1967 main revisions in the dock had been done.
