Gas mileage and transmission replacement

[xplorer66]

I have a 2009 Rogue SL AWD. For the first few years my gas mileage according to the vehicle's computer was 10.8L/100km, or 21.8 mpg. In July of 2013 I needed to get my transmission replaced, under warranty. Since they I've noticed by gas milage is now 12.8L/100km, or 18.4 mpg. Not impressed.

With a 60L tank, I'm fortunate to get 375-450 km per tank. My driving habits have not changed. The vehicle has been well-maintained. I have Michelin Defender tires and check for proper inflation regularly. I live in north-western New Brunswick, Canada if that matters.

Questions:
1) How comparable is this gad mileage to yours? I'm feeling I'm getting worse mileage than the average AWD Rogue.
2) After getting the transmission replaced, could a computer adjustment affect the mileage? Could this be the reason for the bad mileage I'm getting?

All help is much appreciated.

[Rogue One]

Vehicles equipped with engine or transmission computers may require a relearn procedure after the vehicle battery is disconnected. Many vehicle computers memorize and store vehicle operation patterns for optimum drive-ability and performance. When the vehicle battery is disconnected, this memory is lost. The computer will use default data until new data from each key start is stored. As the computer memorizes vehicle operation for each new key start, drive-ability is restored. Vehicle computers may memorize vehicles operation patterns for 40 or more key starts. Customers often complain of drive-ability problems during the relearn stage because the vehicle acts differently then before being serviced. Depending on the type of vehicle and how it is equipped, the following complaints (drive-ability problems) may exist:

• Harsh Or Poor Shift Quality
• Rough Or Unstable Idle
• Hesitation Or Stumble
• Rich Or Lean Running
• Poor Fuel Mileage

These symptoms and complaints should disappear after a number of drive cycles have been memorized. To reduce the possibility of complaints, after any service which requires battery power to be disconnected, vehicle should be road tested.