P47 Thunderbolts of the same era used 70 weight oil, and gasoline was recommended to be added to the oil in severe cold!
That link is very cool! I have all sorts of flight simulators and they are pretty faithful to what is shown here.
P51s had some excellent and some mediocre performance specs, but that was listed with full fuel. And they held a LOT [even without wing tanks]!
When actually AT the far away combat zone, they were much lighter and things improved substantially - they were about as good as you could get at that time with prop planes.