Is there any good reason why my 2.0tdi A3 is consistently 10mpg worse than my previous 1.9tdi A4 ? Lighter body,allegedly superior engine. Computer thing claims I'm getting 39.5 mpg and I actually give this car an easier time than my A4,but it's still 10mpg down. Worth mentioning to the dealer ?? It's barely any more economical than a petrol.