In 2007 the Cat Rep gave us the honest word. ULSD does not probide the neccessary lubricity for diesels and pumps and seals have and will fail. The Factory has to toe or is toeing the line dictated by EPA, just like when they told us small cars are safer than big SUVs with frames. In other words costly bs for Citizens.
He said to run a lubricity additive. There are only tw or three that come close on scoring or wear. Biodiesel was introduced just like ethanol was but a side effect is that as little as 2% bidiesel in your tank will increase lubricity to the neccessary level. The devil in it is that biodiesel will swell and rot seals and hoses especially mentioned hydraulic lift pumps in Cat and Cummins in engines prior to 08 production. I maybe wrong on the age. I noticed in Arizona and elsewhere that Biodiesel is just about all you can find so I fill up with ULSD or ULD if I can find it and add a little biodiesel but no more thant five gallon, in one hundred gallon tank. I wish I had a two hundred gallon tank. It would make the juggling easier. I got the understanding somewhere that to change health old seals and hoses would run over 3 thousand dollars and probably a lot more.
There are studies on lubricity products on the net. I had passed along a couple of them over time but don't know where they are now.
Don't follow the factory/EPA propaganda listen to the experts in the diesel engines and not neccessarily over the road truckers. They just drive them and don't do the maintenance etc.