Agreed, might not ever be needed, but as with most things, prevention never causes one grief. As for those that wonder, does the owner's manual ever discuss microbial growth that can occur in diesel? Hardly ever. How about gelling and icing issues? Nope. I would be willing to bet that the folks who actually wrote the owners manual (usually a 3rd party from the manufacturer), couldn't tell you that there are microbes that set up home in diesel occasionally and generate algae formations that can clog fuel filters and destroy pumps and injectors, especially in fuel that sits for extended periods of time. I have seen dedicated lube and fuel manuals from manufacturers that barely touch on the subject, but those of us who are highly dependent on diesel for business have a close familiarity with diesel issues that can occur when fuel is left untreated. Always a joy to change a fuel filter along side the road at -20F because the fuel decided to solidify because the fuel station didn't have the foresight to have their diesel blended and prepped in advance of the approaching cold weather. The approximate 1-2 cents extra cost per gallon for me to treat my fuel is worth every penny.