I purchased a 2008 Tahoe LT1 at the beginning of September. As of today, I have a little over 2600 miles on the Tahoe. I have taken 3 round trips to and from Charleston, SC from NC. As far as mileage, I get between 18 - 19 mpg in mixed city/highway driving. The last trip from Charleston, I filled up and gotten an average of 23 mpg on that tank. Since I got back, the average has been going down but is still over 20 mpg.