I don't know enough about stuff related to our buses to have an opinion, but I do know that a lot of moisture is generated by running an engine. When it is a cold day you can see that moisture coming from the car exhaust pipe.

That moisture gets into our engine oil. It forms acids. The best way to drive it from the oil is to bring the entire engine up to temperature and allow that moisture to evaporate.

Dale may be getting his engine up to operating temperature by running it at high idle for 30 minutes. I would guess that it gets pretty warm and even if all the moisture is not evaporated, by re-oiling all the surfaces he is likely having a beneficial impact. But that is a guess.