All you are doing is adding moly to one of the moly richest hdeo dinos and making a thick 15-40 thicker. I thin 15-40 delo with 5-20 Chev or Havoline and I use the delo specifically for its better ( than car dino) add-pack. Take another look at delo in the virgin oil tests section.
There is a reason Chevron doesn't sell delo for 49 cents a qt. IMO Valvoline addpacks aren't worth adding to Chevron or Havoline oils.
What I don't get is why Valvoline doesn't use more of its VSOT addpacks to its own oils to make them worth their higher price.
Oh making delo 20-50 is probably lethal viscosity for your oil pump in NJ this winter.