My 2005 Mazda 3 5-door averaged 34mpg on the highway, while my 2008 Mazda 3 5-door averages 28mpg on the highway, what is up? The cars are equipped exactly the same except that the 2005 had a sunroof, both have the 2.3 motor and 5-speed.

Any ideas why there would be that great a difference between the two, and by the way that is with the same aftermarket wheels and tires on both.

Tom

 

vehicle variation for engine tolerance is one...
guessing it has the most to do with the O2 sensor accuracy and calculating the air/fuel ratio.
there is a thread on vehicle MPG here somewhere, and a link to someone's site that logged users actual MPG as well.
I get ~29-30 on average, very steady from day one minus seasonal variation due to temperature.