Reddog, you might be surprised as to how many use a fuel additive in their big rigs. I know I use Diesel Kleen about evry 3rd fill up. It raises the cetane in diesel and cleans the injector. Improves fuel mileage just a bit and lubricates the injectors more. With USLD, it cannot hurt anything. It is cheap insurance.
On my silverado< i use Startron everytime I fill up the truck. Only takes an ounce or 2 and it is an enzyme that prevents the bad things from happening to diesel fuel. I do not drive the silverado that often, so I use it primarily for the protection.