Jim, I don't know why they went to 5 cyl. in those models. The same engine is also used in some of the bigger frame skid steer loaders. I can't tell you if they changed anything or not from the engines in the 5020 and 5025 series tractors or not. The 5 cylinders that were in them were junk. Those same motors were also used in a few of the 300 series skid steer loaders. All of them would leak water around the water pump( can't replace just the pump, its built into the front cover), Leak at the intake/valve cover, melting pistons, injectors cracking etc. I just can't see what was suppose to be better about these engines????