8iron wrote:
150k lifespan in medium duty trucks? Do you have a source for this?
No source = made up.
1st of all, 150, 250, vast majority of 350 (non dualies) are not Medium Duty trucks.  
https://en.wikipedia.org/wiki/Light_truck
Light duty trucks have payloads less than 4,000 lbs. 
The best I've got is the Ecboost torture info here where they say they tested it to 150k:
http://news.pickuptrucks.com/2011/01/what-the-inside-of-a-torture-tested-ecoboost-v-6-looks-like.html
You also need to look no further than the service schedule in your own truck - notice where it stops.  That is generally the design life.