My new 2011 5.3L with 3.42 rear gets 13.5 mpg at best. Pulling a trailer, it will go down to 9.
My wife's 2008 Yukon Denali with 6.2L and 3.42 rear gets 17-19 and we usually have it loaded with our son, his wife and 2 kids.
My next Silverado will be a 6.2L and hopefully sooner rather than later.
I enjoyed reading all your comments. You sold me!
Karl