After I quick research on 2011 Mazda cx 9 spec, I found a article on caradvice.com which stated "Mazda says fuel economy improvements were a result of work done on the models AWD differential gear control, engine optimisation for better combustion control (during deceleration and at idle) and...
I found out that the gas mileage on the 2011 Mazda Cx9 Front wheel drive model is rated at 17 City and 24 Highway. The numbers are slightly higher than 16 city and 22 highway for the 2010 Mazda cx9 Front wheel drive model. I wonder if the Mazda dealership is able to update the engine software...