I just purchased an used 10 AWD 3.6 wagon and my gas mileage has been horrible so far. I purchased the car in Seattle area but found out that the car actually came out of Canada. I live in Oregon at an elevation of about 3000'. Does it take time for the ECU to recalibrate to my elevation, etc? I have driven the car back over to the Valley area which requires going over a mountain pass. That entire trip I didn't get over 20 MPG. Here in town I am averaging about 12.5. The best the dash has read is 13.5. While I know the AWD is going to use some gas, I feel I should be getting closer to 16. I'd ask my local dealer but any time I ask them something about the car they tell me "that's just how it is". I am going to change the filter and plugs soon so I'll see if that makes any difference. I am also used to running premium fuel as all my other cars require it. I noticed reading the manual for this car that GM only wants regular fuel. Can that make a difference? I have been putting in premium. Next tank I am going to try regular and see if there is any difference. Thanks in advance for the input.