Additives, additives, additives. Everybody has their claims, and their research to back them up. ULSD has less lubricity than the old #2 diesel. Fuel additives to boost the "cetane" rating will only make the fuel burn quicker and will not increase you mileage. I've talked to alot of diesel users and mechanics; who say "lubricity" is what you want instead of higher "cetane" rating. Old school says to add a quart of "AFT fluid" about every three tanks of diesel. I've tried it all and even Stanadyne doesn't seen to make much difference in mileage, but I think it helps to lube the injectors etc. I owned a 03 F250 7.3L diesel and got 15mgp towing a 37' toyhauler. Traded it for a 08 F350 6.4L. What a mistake. Now I'm down to 9.5 towing a 35' Razor toyhauler. The new diesels have been chocked down so bad with all the EPA stuff that the engines will not perform to their ability. The new FORDS CANNOT be chiped, change the air intake or exhaust or FORD will cancel your warranty. The new computers have a memory, so if you make any modifications it will show up the next time the dealer plugs in their engine analyzer. What a bunch of bull. It's MY truck, but I'm NOT allowed to set up the engine the way I want. Just more and more control!!!!!!!!!!!!! Who knows what the answer is, but with diesel over $4 a gallon something needs to be done.
