The Russian frigate Neustrashimy is crawling towards Balticsk on a dying engine after it was spotted off Edinburgh on October 22 spewing thick black smoke, then slowed near the Denmark Strait on October 26.
Gas turbines on this type of frigate don't smoke like that, so the smoke and slowdown indicate a loss of engine power from incomplete fuel burn rather than bad fuel, like the ship actually spent her engines trying to limp home.