Sitting to long.
Well, I should apologize. There is a better than average chance that it wasn't Costco at all. I purchased a truck that has been sitting around since July (Build date). More than enough time for what little fuel it had to go bad. The dealer topped it off from less than a 1/4 to full. So for that, I apologize to Costco and you all for the misleading post.
I did go down to Costco and fill a glass growler 2/3 with Diesel before getting yelled at by the attendant since it wasn't an approved container. Poor fella about had a heart attack until I told him it's only diesel. Anyway, the fuel in the glass jug looked beautiful.
I siphoned 15 gallons out of the truck and drained the separator. I replaced the old stuff with fuel from another name brand station. I will be draining the separator tomorrow to see what there is to see. If it runs clean, I will replace the filters and hopefully, no further issues.
Thanks for the ideas and help. You are all helping me figure this out. Merry Christmas!
2017 F-350 6.7L
FX4 Crew cab short box
Build Date July 17