Spy photographers recently captured this Ford F-150 testing in Dearborn with a camouflaged bed, Venturi exhaust tip, and of course a new diesel engine.

With Ram taking the full-size fuel economy crown at present (29 mpg in 2WD form) with its 1500 EcoDiesel pickup (read our test of that truck here), Ford clearly looks to jump into the battle with a turbo-diesel of its own in the to new aluminum-bodied F-150 line.

Although Ford has a 3.2-liter five-cylinder Power Stroke diesel that could work well in this application, being that it’s already been federalized for its Transit vans, insiders say the company will use the Lion V6 engine instead. This 3.0-liter unit is basically what Jaguar Land Rover has just certified and introduced in the U.S. market for the Range Rover and Range Rover Sport Td6 models. The engine, in that application, is rated to produce 254 horsepower and 443 lb-ft of torque.

It is also expected that the diesel is slated to use the new 10-speed automatic transmission that will debut in the 2017 Raptor. It’s possible this engine/transmission combination may push its efficiency higher than the Ram and into the 30 mpg territory. Currently, the mid-size Chevy Colorado and GMC Canyon four-cylinder turbodiesels have the most fuel efficient truck in the market at 32 mpg, and it’s possible this new diesel F-150 could compete even with that figure.

We expect the diesel F-150 to go on sale sometime after summer 2016, along with a recently announced hybrid F-150 in 2020.