Funny that most of the repair centers say not to use fuel additives. I've been running cetane boosters since I had a injector failure on my 6.0 PSD back in 2007. At first I had some issues with the D4 airtronic...dirty screen. After that I replace the glow plug and cleaned the screen. My routine (now) is run the heater hot/high of about 15 min, then ramp it down for the night. It takes a bit of testing to figure out where to set the round thermostat dial to get the temp you want. I ALWAYS set the temp to high before shutting it down and turn off the timer button which automatically defaults to a final 15 min timer countdown. I just leave the doors open and let er run on high until it shuts itself down.
Other than the Airtronic, the Hydronic water heater threw me for a loop after I first got my van. What I found is to ignore the failure codes and let it restart on its own (if it will). It might take several starts each time throwing a code but usually will fire up on its own. I kept trying to stop & restart it. WRONG! Let it go through its cycle. If the display goes blank, wait before you try to restart. It surprised me. I thought it was off then all of a sudden several minutes later it fired up on its own and ran normal.
I will say (at least for me) that some say to run both monthly. I just fired up my Airtronic for the first time since early 2017.
Yeah, so long since I've camped It fired up fine. Still it's a good idea to run it often. I do run the Hydronic every few months in the summer though, and way more in the winter to keep pipes from freezing. I've have the timer set to kick on during those cold days below 28* at 4:30AM & run for 2 hours.
I've ran Fords Cetane booster, Rev X, and finally for the last couple of years, Archoil. It works great.
Lastly I can't say how SMB sets yours up. I put SMB through hell trying to figure out what was wrong but after learning out how to operate the systems, no issues whatsoever. YMMV. Also Jeffery's post is well worth a look. His issue was related to exhaust/intake problems. I've yet to have that give me trouble.
Hope this helps.