Extended warranty on new truck?

The extended factory warranty is well worth the money in my experience. It's also transferable, so any warranty left when you go to sell the truck is viewed as a plus by any potential buyer. With some shops charging $130+ per hour and the repair cost (not to mention the unreliability) of current emissions systems, to me it's a no brainer.

And yeah, any 3rd party warranty is just a money maker for whoever is selling it.

 

For a new truck with a Cummins engine, how is the extended Cummins engine warranty interpreted? e.g. If i'm looking at purchasing 3 years 600k km warranty, does it start AFTER the factory Cummins warranty of 2 years 402k km expires? Or from the initial date of service of the truck?