Well, there is some truth to the computer learning your driving style and adjusting for it. The 5 year thing, he was probably trying to say that after 5 years which should ad up to about "50,000" miles, yer mileage will increase. Diesels typicaly take about 50K to realy loosen up and give better mileage. He just didn't say it to well, that the general public could understand him.
Steve, Pat, Hakbar, & Root Motor
2007 National RV Pacifica 36'