Raw production figures did not measure the naval fuel actually available. Oil varied in quality and competed with power stations, factories, vehicles, and allied requirements, while German ships had sometimes demonstrated performance using superior Welsh coal that wartime supply could not reproduce. Practical fuel differences could cost individual German ships roughly one to two knots, although the figure varied by hull. Synthetic fuel was not an effortless substitute because it required suitable coal and an energy-intensive conversion process.
Notable Point · 2:14:53-2:17:46
Fuel quality behind German trial speeds
Paper access to oil or exceptional trial coal did not guarantee enough suitable fuel at the fleet, industrial, and national levels.