I just purchased a 2003 Dodge Ram 2500 QC LB 4X4 with 87K miles that has a 2006 5.7L with 25K miles. Thus far, I am averaging ~10 mpg, and dealer said I should be getting 12-14 mpg. Not getting any error codes, and engine sounds strong when running. Dealer said there was not real 'diagnostic' they could run to see if everything was ok. Seeking any suggestions and feedback as to first 'why' this may be happening, and 'what' I can do to improve the mpg's. Thanks