My 2007 5.9L Cummins 3500 dually, with cold air intake and TS Performance MP-8 MaxPower chip was yielding 20 mpg highway (trips) with 3,500 lb camper. At 35,000 miles I took it in for "Recall" (california smog adjustment they said). Dumb Dumb move I think! Mileage even with TS chip is now 16mpg hwy!!! What do I do now? Help anyone?

 

What exactly did they do to the truck, reprogram, or installed new parts?

 

Are you hand calculating or going off the overhead?

 

They reprogrammed only. I am going by overhead, but last I checked it was pretty accurate?

 

They call them things the "Lie-O-Meter" for a reason.

 

Does anyone know if the computer chips, like TS Performance MP-8 MaxPower, overrides the dealer programming? I thought it did, but now I am not sure.

 

Some are more accurate than others. Mine is within about .5mpg compared to hand calculation.

 

20mpg in a dually with a camper sounds a little optimistic, 16 sounds more realistic. Hand calculate a couple of tanks and see where you really are. Do you pay any attention to your miles per tank when you fill up? Getting fewer miles on a fill up?