Low fuel temp.
Many years ago I was flying the old IL-18. Of course it was in the winter of 1990, January to be exact. Fueled home then in Shannon than in Keflavik. Then what???? Aha so next came the beautiful sight of Greenland and in my mind came the big question does them stop or not? The type in the epoque had .3% super anti-ice liquid in fuel. Because we did not added 'I' liquid at the last two fueling stops, my hart gone small. I was flying to Gander like a ghost. Never ever from that moment on I didn't ignore the fuel temp. gauge.