Have you lost a lot of weight?-just kidding-Have you changed fuel brands or driving habits? Other than that,with 175,000 miles,it's probably just a blip,but at least it's one in your favor.Other factors include,but are not limited to,tire pressure,alignment,various changes in mechanics of the vehicle(lubricants,service frequency,emissions control functions and upkeep)and of course,how much weight you carry and how you drive.Your overall milage seems right-on for a Sprinter.