They probably get around 8mpg with the stop and go. The International gets 7.5-8mpg, the 4500 gets 8mpg.........everything is around 8mpg. My '02 pickup w/ 6.0L gets 8.5-9.5 with a trailer behind it but that wasn't stop and go lawn mowing driving. My '07 DMAX gets 14mpg around town and 17mpg highway but I think I've got a bad injector. I've added a programmer and 4" exhaust from the downpipe back, deleting all of the re-gen/cat junk and should be getting 20-22mpg highway.