Technical advances in diesel engines and drivelines.

What are you looking for? The efficiency isn't enough that you would notice it on the fuel card, let alone pay for the newer machine. More power? Maybe on paper, but where are you going that you need that little extra? More reliable? Man I don't know about that. Lots of high tech expensive stuff on the new ones to go wrong. How much more reliable than an old diesel with no plugs to change are we going to get?