I have heard that the additive they use for lubricity is not added until it gets to the distribution point,,,,,where ever that may be!! So there are lots of different people adding lubricity and you really never know if they have skimped on how much they put in.
When diesel had all that sulper in it, it really lubed the engine, which is one of the reasons diesels lasted so long. The other reason was low rpms.
But in my shop, we are seeing things like rocker arm assemblies seizing up, hash marks on the cyl walls wearing off much too soon, etc. Not only have they taken the sulper out of the fuel, but for the sake of the DPF, they have removed things like Calcium and potassium from the oil, as it causes ash in the DPF. So we have also lost lubricity in the one thing that was meant to lubricate the engine.
Opti lube also makes an Oil fortifier, that puts a lot of the "Slippery" back in the oil.
It only requires use at oil changes instead of at each fill up. I think this is a really good idea, especially for older trucks and deleted ones as well. ")