Re: 1999 Cummins 5.9 pm check list???
in my opinion, the 5.9 cummins is one of the most fuel efficient skoolie engines, but a lot of it depends on the rear end gear ratio, and the transmission.
The AT545 trans does not have a lockup torque converter, while the mt643 does have lockup converter.
A cummins 5.9 with 4:10 rear end and trans with lock up torque converter will easily get 10 mpg. At 60 mph it can even get 12-14 mpg.
Quis custodiet ipsos custodes (who will watch the watchmen?)