recently changed all of my 2007 Land Rover LR3 HSR O2 sensors (Bank 1 and 2, upper and lower). Went to the Land Rover dealer to get the check engine light assessed and reset. After getting everything reset they took it for a test drive, did another assessment and found no more faults.

Now for the issue. My fuel efficiency has significantly dropped. I was previously getting 425-450 miles per tank with 17 mpg (city) and 20ish mpg (highway). I am now getting 350 miles per tank with 12-14 mpg (city) and 15 mpg (highway). I've added Lucas Upper Cylinder Lubricant to see if that will help the fuel efficiency. It did not.

Where re do I go from here?