There are a couple of diesel fuel stops that may work for you in W. Yellowstone. One is a Chevron on the highway coming in from the Idaho side, but you may have to back out. The other is just as you turn to head North out of town towards Bozeman. If you're coming from the Idaho side, there's a roomy pull through diesel gas station on the East side of the highway in Henry's Lake and another on the West side.
2011 Bighorn 3055RL, 2011 F350 DRW 6.7L 4x4 Diesel Lariat and Hensley TrailerSaver BD3, 1992 Jeep ZJ and 1978 Coleman Concord Pop-Up for remote camping
Dave & Renee plus (Champ, Molly, Paris, Missy, and Maggie in spirit), Mica, Mabel, and Melton