Attention: TDR Forum Junkies 
White Ram1 said:
If could only pick one reason I'd say it is because DC has to dance to the tune of the government fiddler. In other words, they tune the computer to what the government wants, and not what the customer wants or what makes the truck operate the most efficiently. We know from the performance of these engines over the years what they are capable of--20+MPG every day of the week. I doubt that DC would purposely be turning down the performance and efficiency unless they were complying with some mandate.
