What is the Real MPG for 2011 Tahoe and Yukon Non-Hybrid?

I am in the process of shopping for a new car. I am currently in a small SUV that seats 5 and need to upgrade to a larger one (family of 5 + German Shepherd.) I am thinking about the Yukon or the Tahoe but I would like to here from real owners what kind of gas mileage they are REALLY getting. You can never trust the stickers and the dealer estimates.