Who's studies ?
Funded by ?
Hopefully NOT the aftermarket additive companies....
Sure, a lot of people put a lot of STP in their vehicles for a LONG TIME in the belief that even if it didn't do any good it wouldn't do any harm and maybe it would do some good... on and on.
There was an independent study by me, myself, and my 92' Cummins, when ULSD first came out. In which I didn't put a fuel additive, such as Power Service, in the tank before I filled it. So because of the fact that when you take all the sulfur out of the diesel fuel, you take away the natural lubrication properties, (and don't think for a second that the sulfur doesn't add a lot of natural lubrication because you are
dead wrong, think of what happened with gasoline when they took the lead out of it.), so it caused my injection to immediately begin a slow consistent drip. The lack of lubrication killed the rubber seals in the IP, and to the this day still does it.
If you feel other wise about it than I suggest you go read any diesel forum, and search for the introduction of ULSD, and see if the refiners really have, "made up for it in the mix". You'll find pages of reading material that will last you for more time on the toilet than you have left in your entire life time.
Personally you sound like a tree hugger, not that I have a problem with keeping the environment clean, I just have a problem with people preaching there beliefs on people when it's unwanted. You do realize that diesel engines are greener and more fuel efficient than a gas engine ever will be, even ones that are 20 years old that have no emissions what so ever. The tail pipe might smell a whole lot worse than a gasser, but we use much fewer gallons of fuel compared to a gasser over the same distance
To the OP, I would expect when they mean not to use a high sulfur content fuel and that it will decrease the length between oil changes, they mean if your are using a CJ-4 API rated oil in the engine. Cj-4 oil was designed around ULSD (15 ppm), running a higher sulfur content fuel with it will cause the oil to break down much more rapidly. But since it says to run a low sulfur fuel anyway, I would stick with ULSD. As far as a fuel additive, yeah, I would run some. I use the white bottle of Power Service all year round in my tractor because it has anti-gel properties for cold weather. In the trucks I'll alternate between the gray and white bottles. I have run Power Service for the past 4 years and have great success with it.