Haven't heard anyone say better mileage. Kept injectors clean, fuel moving. Years ago we w ould gell up and be dead on side of road. I would use fuel additives for peace of mind.
You sent me on a mission to Walmart I went purchased 4 gallons of the stuff, then looked up the web site and posts had people saying how it improved their mpg. Not sure about oil additives if they really are good for a new truck or not.
I use Lucas in my motors and in the truck transmission. I also use the Power diesel fuel additive because it lubricates and keeps the system clean, and my injectors don't foul up. I don't really know if my mpg is any better, but the power is. You need all you can get when running a 210 CAT.