Besides, there's something the Series 60 seems to have more of than the MB4000, and that's TORQUE, every trucker's first (sometimes second, but we won't go there just yet) love. At least that's the consensus(sp?) of the local milk haulers. The MB unit is OK as long as there aren't too many serious hills involved. But keep in mind that all this is w/full 80,000 GVW loads. In an RV situation it might all be immaterial, though the parts and service situation, as Geof says, is way better with the Detroit 60, having been around about 15 years(has it really been THAT long?!?!). Happy hunting!