Oil heater
 

Was just watching a new dodge ram commercial, and apparently they heat or cool the oil to stay at 190degrees for peak efficiency. Anybody hear of this? Snake oil?

My diesel has it.
Bypassed coolant exchanges heat with the oil. It heats the oil during warm up and cools the oil when the engine is warmed up to operating temperature.

Ultralight duty gas enignes in cars and most trucks don't have this.
Its a diesel truck thing and its not a new idea.

You want the oil to be in the engine's proper operating temperature range. I always figured 212F was "right", since that's where the "high temp" tests are done on motor oils. Some people like 180F, I always figured that there the oil would take longer than I like to outgas the water in it, which also pointed to 212F.

A number of cars through the years (mostly ones with sporting pretensions) have had oil/coolant heat exchangers. There was an optional one on some Civics (the factory manual for the 88-91 CRX shows it) in between the oil filter and the engine block, and the Porsche 944 had a separate one. Those would warm up the oil when the engine was cold--the coolant heats up a lot faster than the oil does--and keep it at operating temp when it started to get too hot.

So yeah, a known thing.

-soD