Mine is completely stock and is getting better and better on mileage the more I drive it. The overhead console says 19 mpg right now. This is some city driving and county road driving (55-60 mph). Almost 6,000 miles on it now.
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09 Ram 3500 QC LWB SRW Bighorn
02 Chevy 2500HD D/A CC SWB
00 F550 PSD