It's an issue of the powertrain. Look at the other applications of the MZR: the Mazda 3 and Mazda CX-7, for instance. The 3 is slightly lighter and more aerodynamic than the 5, while the CX-7 is less aerodynamic and roughly similar to heavier weight.
2012 Mazda5 - 21/28
2012 Mazda3 hatch - 22/28
2012 Mazda CX-7 - 20/27
Simply plopping in the Skyactiv powertrain in the 3 of the same year yields outstanding improvements in economy:
2012 Mazda 3 2.0Skyactiv hatch - 28/37
All Mazda needed to do was shove the same powertrain in the 5 and we'd have an amazingly efficient little people and cargo mover. I imagine the results would be something like 27/36. If I keep this thing around for a while, and I can get a place with a garage, I might spend the money to pick up a used 2012/2013 2.0 Skyactiv engine and transmission from a 3; it should nearly just drop right in.
2012 Mazda5 - 21/28
2012 Mazda3 hatch - 22/28
2012 Mazda CX-7 - 20/27
Simply plopping in the Skyactiv powertrain in the 3 of the same year yields outstanding improvements in economy:
2012 Mazda 3 2.0Skyactiv hatch - 28/37
All Mazda needed to do was shove the same powertrain in the 5 and we'd have an amazingly efficient little people and cargo mover. I imagine the results would be something like 27/36. If I keep this thing around for a while, and I can get a place with a garage, I might spend the money to pick up a used 2012/2013 2.0 Skyactiv engine and transmission from a 3; it should nearly just drop right in.