I recently got a chance to drive the new 2015 Ford F-150. For those who haven’t heard, the big news for Ford’s half-ton is that the cab and bed are made out of aluminum rather than steel.

Ford says the new F-150 is up to 700 lbs. lighter than the outgoing truck, with around a quarter-ton of that attributed to the aluminum body. The primary benefit of the F-150’s crash diet is fuel economy, since a lighter truck needs less power to propel it. Ford is taking advantage of the F-150’s lighter weight by making changes to the engine lineup: They’ve replaced last year’s entry-level 3.7-liter gas V-6 with a 3.5, and they’re introducing a new 325-hp 2.7-liter EcoBoost twin-turbo V-6, which they say will do the work of a small V-8.

It all sounds promising, but the EPA hadn’t published the F-150’s official fuel economy ratings at the time we went to press, and neither had Ford. (They’re also remaining oddly tight-lipped about the F-150’s actual curb weight.)

I’ve sampled several of Ford’s EcoBoost-powered cars and SUVs, and while I’ve achieved excellent economy with the bigger engines—the 3.5-liter turbo V-6 in the Ford Flex, for example—I’ve had less luck with the smaller ones, such as the subcompact Fiesta with its 1-liter turbocharged three-banger. Small as the Fiesta is, there’s no way to propel it on one liter of displacement without leaning heavily on the turbo—and with gasoline engines, boost kills fuel economy. There’s a point of diminishing returns with a turbocharged gasoline engine, and it remains to be seen on which side of the line that new F-150 will sit.

The irony here is that there’s a perfectly good solution for fuel economy in a half-ton truck: the diesel engine. The proof can be found at your local Chrysler dealer in the form of the Ram 1500 EcoDiesel, a steel truck with a 3-liter turbodiesel V-6. EPA fuel economy estimates are better than any other half-ton truck at 20 mpg city, 27 mpg highway, and 23 mpg combined, and the handful of owners from whom we have heard are averaging in the mid-20s. (I’m about to take a road trip in one of these trucks, and I’ll let you know how it goes in next month’s column.)

2015 Ford F-150

Diesels shrug off weight in a way that gasoline engines don’t. Look up the EPA fuel economy estimates for Volkswagen’s diesel-powered cars, and you’ll find that the 3,100-lb Golf TDI’s numbers are only a hair lower than those of the 3,450-lb. Passat TDI. The Aluminum Association states that an aluminum diesel vehicle should be able to achieve a 13.1 percent increase in fuel economy compared to a steel-bodied vehicle, but the narrow difference between the Volkswagens would call that into question. Alas, since the 2015 F-150 will only be offered with gasoline engines, we won’t get a chance to find out.

The F-150’s aluminum body has other advantages besides fuel economy. Chief among them is capacity. Since the gross vehicle weight rating (GVWR, the maximum permissible weight of the truck, its occupants, cargo and fuel) and gross combined weight rating (GCWR, similar to GVWR but including a trailer) aren’t changing, 500 lbs. less curb weight equates to 500 lbs. more carrying capacity.

But aluminum also has disadvantages. For one thing, it’s trickier to repair than steel. Welding aluminum requires special skill, and bolting it to a dissimilar metal can lead to galvanic corrosion. Ford plans to train hundreds of new body shops, but collision repair choices will still be limited. The costs for Ford to move to aluminum construction can’t be cheap, but unlike a diesel engine, which can be offered as an extra-cost option, Ford can’t pass those costs on to the consumer—they still have to be price-competitive with GM and Chrysler.

I do think we’ll be seeing a lot more aluminum-bodied, particularly cars and SUVs. But what about heavy-duty pickup trucks? I don’t think that will happen anytime soon. Automakers are not required to publish EPA fuel economy estimates for vehicles with GVWRs over 8,500 lbs., and considering how much brawn modern-day HD pickups offer—most can be configured for a 3-ton payload—an an extra few hundred pounds of carrying capacity won’t make much of a difference. Given those factors, it would be difficult to justify the added cost of aluminum.

Besides, we can’t expect the steel industry to take this whole aluminum onslaught lying down. Automakers are already making more extensive use of high-strength steel to save weight; in fact, about 50 lbs. of the F-150’s weight loss come from improvements to the steel frame. I’m sure we’ll see new steel technology that will give aluminum a run for its money.

Bottom line: it’s great that Ford is embracing a new way of thinking, and I’m hopeful that F-150 owners will see serious savings at the gas pump. As for me, I’ll stick with my steel-bodied diesel.

Thanks for reading Diesel World, and I’ll see you out on the road! DW

2015 Ford F-150

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