I heard it rumored to weigh 3600-3700 lbsI average 19-20 around in the C7 with a manual. Freeway 27-28 as I don't use Eco but keep all 8 cylinders operating.
Is the weight of the V known yet. That will have an impact on the mileage. As long as no "gas gullzer" tax I'm OK with what ever the mileage.
My $.02 worth.