Is that hand calculated?????? Most people bone stock are seeing 12-13. With MP-8 or some form of chip some are seeing 15, 16, 17. Again with the DPF delete gaining even more mpg's. Tires size will kill that in a hurry!!!
I have run about 3000k miles on my DPF delete kit and MP-8. I have been averaging 18 mpg. With 305/45-22's (about 33x12.5)
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07.5 - QC - SB - 6.7L - 68RFE - Afe intake - TS MP8 - 5in Magnaflow TBE - Gear Alloy 22x9.5's with 305/45's - Bilstien 5100s - Ultralite 2 gauges.