In two-wheel drive guise, the EPA rates the 2011 Ram 1500 at 14 mpg city and 20 mpg highway for both V-6 and HEMI variants, an odd result that reflects the aging design of the smaller engine and the cylinder deactivation of the HEMI. The 4.7-liter engine rates 14/19 mpg, due in part to its flex-fuel capability. Running on E85, the 4.7-liter V-8 rates 9/13 mpg due to ethanol's lower energy content relative to gasoline. Opting for four-wheel drive, available only on V-8 models, knocks 1-2 mpg off the city and highway ratings for a 13/18 mpg rating with either engine.
The lack of fuel savings with the V-6 makes it a non-starter if you can afford the upgrade to the V-8, and choosing between the HEMI and 4.7-liter is again down to purchase price unless you need and can take advantage of the smaller V-8's E85 capability.