#1D will have less btu's, and MAY have less lubricity than #2D. I live in a somewhat moderate climate where true #1D will not be in commercial pumps. There will be an unknown percentage of #1D and #2D, or a winterizing agent added.
As far as gelling temperatures are concerned, numbers on the web are all over the place. I settled on the following, somewhat conservative numbers for #2D (untreated) :
Cloud point 32f
CFPP (cold filter plugging point) 10-15f (some sources say 0f)
Gels (pour point) at 0f
100% #1D goes south at around -40f
I personally try to use up #2D summer fuel and have November fuel in my transfer tank for the winter. I also add Power Service anti gel additive to ensure I don't have any problems.