Normal
It is actually an FAA code violation to put multiviscosity oil in them!! So you decide to haul fuel to Prudhoe Bay, it goes down to 45 below and the wind is blowing 45 mph because it really isnt blowing very hard that day. deal with keeping it running or deal with putting heat on 4 two row engines to start it. Oh, per the approved manual from the 30's it is acceptable to cut the straight viscosity oil with Fuel, up to about 1/3 of the volume. Multiviscosity oils were never approved for those engines though. So maintenance procedures from the stoneage are still firmly in place. Count on your government for health care too!! (I am surprised barbershops are not still bleeding people.)