Flying J puts the ULSD sign in large letters on the edge of the roof over the big truck pumps. It's usually at one end or the other or the line of pumps. When you look at the diesel prices on their web site you can see they have 2 price columns one of LSD the other for ULSD. Lately the LSD side has been going away. While the price has been identical the LSD seems to be going away. I would imagine that at the stations that no longer list LSD, ULSD is all they have now even at the RV and auto diesel pumps. They are required by EPA now to have ULSD but not LSD.
I now carry a 5 gallon can of B99 biodiesel to add that to the tank to maintain a B2 concentration so that my fuel system gets the lubrication it needs that ULSD doesn't have any more. Three gallons each side is enough for that purpose. Biodiesel is available in most areas and a web site that lists suppliers is online. (
http://biodiesel.org) Since biodiesel (B99) is not contaminated with sulphur it also complies with the ULSD edict from the EPA.