Diesel at very high alts?
NO.
When you're only in -20 C, and want to stay out of trouble, it's not exactly Diesel any more, - being mixed to perhaps 20%.
At -50, you won't even pour Diesel any more, so, I guess it must have been some cocktail.
UNLESS...you keep the fuel and all the oil lines warm, which is quite an effort.
Not done on Diesel engines today, - the Diesel just gets mixed.