Which one should I run? This is what I know. The BP is out of Louisville. All the different brand terminals use Marathon base gas. The shell comes from Zionsville Indiana, close to Indianapolis, but I don't know what base gas they use. Here in southern Indiana we don't have any special fuel requirements nor does the Indy area, but Louisville does. I would think the Louisville gas would be built to Indiana specs but don't know if the base gas has any negative additives.