Ford recently announced its triumphant return to the top of the pickup fuel-mileage heap, with a 30 mpg, diesel-powered, rear drive F-150. That’s a full three miles per gallon better than the prior record-holder, the Ram 1500 diesel.

2019 F-150 (not a diesel)

If you’re a 4x4 buyer, though, you’re better off sticking with the prior Rams — because the 2018 Ram 1500 was rated at 27 mpg on the highway, whether it came with rear wheel drive or four wheel drive. The Ford’s 30 mpg rating drops down to 25 mpg (highway) as soon as you order four wheel drive.

What’s the reason? It’s not the transmission; both Ford versions have ten-speeds, and both Ram versions have eight-speeds (gear range is similar, so the difference in gears isn’t a major differentiator). Ford’s diesel has 250 hp and 440 pound-feet of torque, edging out Ram’s 240 hp and 420 pound-feet.

Could the difference be due to the Ford’s big lift? A regular cab F-150 4x4 is 1.4 inches taller than the rear-drive version; that gap gets bigger as you move to eight-foot boxes (1.8 inches), SuperCabs (1.5 to 1.7 inches), and SuperCrews (1.5 to 1.6 inches). If Ford didn’t adjust the aerodynamics to match, it would cause enough drag to slam fuel economy, especially if the system was tuned more for good EPA numbers than good day-to-day mileage.

Ford also still has a much better city rating.

Ram, incidentally, has a roughly 0.6 inch lift for its 4x4s, which could explain why their highway economy on rear- and four-wheel drive trucks is the same, at least when rounded off. Here’s a table showing the city/highway mileage for the two trucks, with different driven wheels:
Ratings for the 2019 Ram 1500 are not out yet, except for the Hemi V8 non-hybrid option. The company will be launching hybrid V6 and hybrid Hemi pickups after the initial run, followed by the diesels. The company has not said anything on the record, but it seems likely that the next-generation diesel will have higher power ratings and/or fuel-economy ratings.

Ford’s announcement could be bad timing for Ram, which is selling 2018 Ram 1500 diesels while waiting for a second-generation engine — even if the 4x4 is a common choice. The Ford has around two thousand pounds over the diesel Ram 1500 in rated towing capacity,  opening it to more trailer owners.

Still, Ram is still king of the hill in highway mileage for 4x4s; and a second-generation V6 diesel, reportedly on the way for the end of the 2019 model-year, may well bring them back to their earlier leadership role.