It was one of the biggest questions about the 2015 Ford F-150: How would the truck's aluminum cab and pickup bed fare in today's rigorous safety testing?

While aluminum has been used for the bodies of several luxury cars before now, Ford's decision to deploy it on the best-selling and high-volume F-150 generated spirited discussions about the metal's potential faults.

Critics said aluminum could be less durable than steel, wouldn't perform as well in crashes, and would be more expensive to repair afterwards.

DON'T MISS: Aluminum-Body 2015 Ford F-150 Gets 5-Star NHTSA Rating For Crash Safety

Now, the first crash test results from the Insurance Institute for Highway Safety (IIHS) will likely give buyers and analysts more to talk about.

The IIHS found that aluminum provides as much protection as steel--but its test results for the F-150 itself were mixed.

The four-door F-150 SuperCrew model received "good" scores--the highest level achievable--in all IIHS tests.

2015 Ford F-150 aluminum body shell

2015 Ford F-150 aluminum body shell

That includes the relatively new small-frontal overlap test that has flummoxed several other makers and led to "poor" scores for some older models.

Accordingly, the IIHS dubbed the F-150 SuperCrew a "Top Safety Pick" this year--a coveted award.

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However, Ford's F-150 extended cab model--which only has a small rear seating row and half-size doors--did not score as well.

This model received "good" scores in the moderate-front overlap, side, roof-strength, and head-restraint tests, but only a "marginal" score in the small-frontal overlap.

The IIHS says Ford added structural elements to the SuperCrew's front frame to improve its crash-test performance, but did not add them to the extended cab.

2015 Ford F-150

2015 Ford F-150

Apparently, SuperCrew buyers will be getting a little more than two full-size rear doors for their money.

The IIHS also compared an aluminum 2015 F-150 to a steel-bodied 2014 model in two crash tests.

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"In both test scenarios, the aluminum F-150 had more extensive damage than the steel model," researchers said.

Total repair costs were 26 percent higher for the aluminum model, the IIHS calculates.

Extra time needed to make repairs to front-end damage, and higher parts cost for the rear damage, accounted for the increase.

2015 Ford F-150

2015 Ford F-150

Ford vigorously disputes that conclusion, however.

The carmaker released a pointed statement saying it "does not agree with the repairability costs and findings by IIHS," referring to the tests as "crash stunts orchestrated by IIHS and others."

It cited results from body-shop certification company Assured Performance showing average repair costs to be $869 less than steel 2014 models.

MORE: 2015 Ford F-150 Team Fights Fear Of Aluminum Toughness, Repair, Cost (Apr 2014)

Ford also claims that insurers Allstate and State Farm says insurance costs for the 2015 model are equal to those of the 2014 model.

It's clear there will be more to this story--as there will be on the real-world fuel efficiency of the lighter aluminum F-150 and its EcoBoost engines.

After all, boosting the big pickup's gas mileage was why Ford went to aluminum in the first place.


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