Phx it’s plain old diesel with no additives, per the tanker drivers.
Costco on the other hand advertises they have “up to” 5% Bio.
I always question when anyone claims “up to”.
There’s only 2 Costco’s in Ariz with diesel.
I deliver fuel for a living, I can tell here in PA the state has Mandated all road use ULSD have at least 2 % Bio IE : B2 but from time to time B5 is cheaper and they will get that.
Sadly gas station do not have to tell you what you are buying. I think at a minimum they should have to tell you if it winterized. You be shocked how many station try to save 15 cents a gallon in the winter and sell untreated fuel.
I also deliver to WVa and Ohio and they get pure ULSD never with Bio in it.