Poor fuel economy..Help!

[grease_mnky]

Forgive a Noob in the forum if this has been asked. I searched may variations and could not find.

I have a 2008 A/S 2.5 CVT. I have driven mostly highway miles with city driving on the weekends. I have about 57K miles on the car. I have been tracking my milage as of late because I thought i was getting poor economy. Well, after three months I am averaging 20 MPG! I have seen several posts that people are averaging 25+ MPG so I am a little upset...

Mods: The only mod on the car is the K&N filter in the stock air box. Stock 16" tires and wheels.

Now for what I have tried...I used the FSM's guide to reset the Accelerator pedal position sensor, the Throttle valve closed position sensor, and the Idle air volume sensor (all without the Consult 3 as i do not have one). I cleaned the MAF sensor, air filter, oil change, and checked the air in the tires. I drive the car like a grandma and dont exceed 65 mph even on the freeways. I also have noticed black carbon or soot on the inside of the tailpipes and on the chrome tips. This leads me to believe the engine is running rich but I do not know how to fix that issue on the computer controlled car.

Any help or suggestions would be great. The local Nissan dealer is kind of an a**hole and wants to charge me $80/hour to diagnose.

Thanks