No full tank math yet on my new to me 05 Escalade w/112k miles but its looking like I will be in the 10s, all hard city. New to me Yukon XL 2WD i don't have a full highway only tank yet but i a half/half on that one looks like 15ish. Premium on Escalade cost per mile right now is about 37 cents. Regular on the 2wd Yukon XL, our highway work hauler, about 19 cents/mile if i can get tank to tank 18 mpg. Its rated for 19 highway so i think thats realistic. The cold, short trips, and novelty of the 6 liter LQ9 are gonna cost me. In the same driving my Alltrack DSG would do 17-18 just for a frame of reference.