Years ago a Dodge Ram mechanic told me that if I wanted to buy a used truck with the cummins that I need to buy a 2007-2009.
My question is why?

 

More displacement and common rail injection. But the 2007+ don't look as good as the second gens. Put a 2007+ Cummins in the second gen!

 

I'm not sure how many years ago you're talking, as those trucks are only 15 years old now. Its hard to say his reason but I wouldn't mind knowing myself. Most people have the mentality of "oh no new release motor, be scared" when in reality all they did was bore and stroke a 5.9 and give good injectors again. The bigger downfall was the emissions side, which really surprises me that he suggested it. EGR, DPF, VGT turbo. Don't get me wrong they're still a very dependable motor and most of that vintage by now have had the problems "addressed".

Keep in mind early model 07 trucks still have the 5.9 motor, but late 07+ is when the 6.7/emissions were installed.

12v guys will fight on this but I think the best Cummins motor to buy is the 03-early 04, got enough power to get out of its own way, good MPGs and reliable injectors. Unfortunately its in the ugliest dodge chassis conceived lol. the 06+ at least looks better

 

Thank you