What is the best diesel additive for increased lubrication?

no use only what the car maker suggest . but sta-bil is good additive

Marvel Mystery Oil, this is a must if you have a 98.5 -02 Dodge Ram. The VP44 is a very precise Injection pump and needs a polymer based lubicaten or the rotor inside of it frys and your 1600$ injection pump becomes a paper weight, w/o proper lube. Marvel Mystery Oil is the best for increasing your lubrication. It's cheap and easy to find too. When ULSD first went into affect my dodge wouldn't do much more than idle until I started using Marvel, it pretty much won't run w/o it if that tells ya anything about this aditive. ATF seems to do a good job on the older dodges, but not the 98.5 on up. It frys Injection pumps. If you want a good cleaner Seafoam works wonders. I've ran pure biodiesel B100 multiple times and it works as well. But hard to come across. Biodiesel with Marvel is a perfect combo. Your injection pump uses diesel fuel as it's lube so it is critical that you have proper luberication

As I mentioned in my answer to your other question, the fuel makers add some biodiesel to improve the lubricity and cetane of the product. It seems to work just fine.

you dont really need to add anything to the fuel to increase lubricity.the cummins fuel pump uses the engine oil to help keep it lubricated. the military uses cummins engines in several of their vehicles,and these trucks are running on jp-8, a cheap grade of jet fuel which has virtually nil lubricity