I have had a A3 2.00TDI Sportback from new and on a daily motorway run of 62 miles was averaging 49-50mpg as per display 1, display 2 giving the total average from new continually went up and was sitting at 47.3mpg . Took the car in for first service at 17000 miles 2 weeks ago and car is now averaging 44-45mpg for same trip and the total average on display 2 is continually going down . Took car back and they did a diagnostics and could find no problems but said they had reset the computer but still same as before . I appreciate that nothing at a service should effect the mpg but was wondering if anyone had any ideas what the problem could be to lose 5-6 mpg for no apparent reason. Car drives normally.