The 2015 Ram 3500 HD Crew Cab Laramie Longhorn 4×4 is first up to take the highway mpg test. It’s being compared against the 2015 Ford F-350 Super Duty Crew Cab King Ranch 4×4.

Naturally, the Ram is powered by the high output 6.7L I6 Cummins engine that makes 385 horsepower and 865 lb-ft of torque. The 6-speed Aisin automatic transmission sends the power down the line.

These two trucks are as closely matched as we have had. They are comparably equipped and have nearly identical weights. The Ford is actually 80 pounds lighter.

They were tested on the same day and same route (back to back). We used the same diesel pump. MrTruck.com (Kent Sundling) filled up both trucks himself and also drove the identical loop in both of these duallies.

The route is approximately 21 miles north-bound and 21 miles south-bound on the stretch of I-25 north of Denver, Colorado.

The trucks were towing the same LoadTrail flatbed tilt-trailer with the 1968 Ford Bronco on it. The total trailer weight is 7,250 lbs.

Dually HD Diesel – Highway MPG

2015 Ram 3500 2015 Ford F-350 Model CrewCab 4×4 Laramie Longhorn CrewCab 4×4 King Ranch As Tested $ $69,910 $67,810 Engine 6.7-liter I6 6.7-liter V8 Transmission 6-speed 6-speed Auto Power (hp / lb-ft) 385 / 865 440 / 860 Axle Ratio 4.10 3.73 Test Load (trailer + ppl) 8,250 lbs 8,250 lbs Ambient Temp F 63F 66F Route (mi) 43.6 43.6 Elevation Avg (feet) 5,100 5,100 Highway MPG 14.20 12.36

Check out all the details in this TFLtruck mpg test video.

Andre Smirnov is a life-long automotive enthusiast, writer, reporter, and software engineer. He has been a contributor at TFL since 2011.