Ford Motor Company (NYSE:F) is inching closer to the launch of its highly anticipated 2015 Ford F-150 pickup truck. The first pre-production prototypes are expected to roll off the line within the next few days, and dealers will start getting shipments before the end of the year, with volumes ramping up in early 2015.

Truck enthusiasts and investors alike have been looking at the new F-150 as a potential game changer in the pickup market. Ford made a bold but risky bet on moving to an aluminum body in order to cut up to 700 pounds of weight from the vehicle. This will give it superior fuel economy.

The 2015 Ford F-150 will offer industry-leading fuel efficiency. Source: Ford Motor Company.

By contrast, top competitor General Motors (NYSE:GM) launched its new generation of pickups last year with conventional steel bodies. With gas prices plummeting recently, GM's decision to play it safe seems increasingly wise. Ford may have trouble getting a big enough price premium to recoup its investment in aluminum body technology.

The fuel economy play

While Ford has not yet released fuel economy statistics for the new 2015 Ford F-150, it is widely expected to offer a big improvement over the 2014 model, as well as over competitors' offerings. Late last month, Ford stated that fuel economy for the new F-150 would be 5%-20% better than the current version, depending on the model.

The best fuel economy will come from the new 2.7L EcoBoost V6 engine. Ford says that this engine in a typical configuration can meet the needs of more than 90% of light-duty truck buyers. Automotive News has speculated that the 2.7L engine could deliver 27 to 28 mpg on the highway.

That would make the 2015 Ford F-150 the most fuel-efficient gasoline-powered full-size pickup on the market. It could also potentially match Fiat Chrysler's Ram 1500 EcoDiesel in fuel economy.

The new Chevy Silverado has a more conventional steel body. Source: General Motors.

It would also put Ford well ahead of top rival GM, even though the latter just released a new generation of trucks last year. A common configuration of the 2014 Chevy Silverado 1500 carries a 16 city/22 highway mpg rating. (The ratings can fluctuate by up to 2 mpg in either direction depending on the choice of engine and 2-wheel drive vs. 4-wheel drive.)

Fuel prices are falling

Not too long ago, making a big bet on fuel efficiency for the 2015 Ford F-150 seemed like a no-brainer. However, oil prices have been plunging lately, leading to lower prices at the pump across the U.S. As of Friday, the average retail price for regular gasoline was $3.144 per gallon, according to AAA. That was down from $3.373 per gallon just a month earlier.

Mid-grade and premium gasoline prices have fallen by a similar amount. Moreover, based on the normal seasonal decline in gas prices and the recent drop in world oil prices, the national average for regular gasoline should fall below $3 per gallon within a few weeks.

Indeed, the wholesale spot price for gasoline in Los Angeles has fallen from an average of $3.169 per gallon in April to just $2.268 per gallon as of Tuesday. If oil prices remain near recent levels, some parts of the country could even see gas prices approaching $2.50 per gallon in the next month or two.

There's no way to know how long oil prices will remain depressed. They could snap back soon due to supply disruptions in the Middle East or Africa. However, if oil (and gasoline) prices remain low, the 2015 Ford F-150's superior fuel efficiency could be a smaller advantage than what Ford was counting on.

Can Ford boost prices?

This is a critical point, because Ford needs to boost its average transaction price to justify the massive investments it has made in changing to an aluminum body for the F-150. The base prices of the 2015 Ford F-150 are rising anywhere from $395 to $3,615, and Ford needs at least this much incremental revenue to offset its material cost increases.

High-trim F-150 trucks can already cost far more than $40,000. Source: Ford Motor Company.

On one hand, lower fuel prices could make pickup buyers feel like they have enough extra cash to a buy a more expensive truck. On the other hand, if Chevy and Ram offer pickups with traditional steel bodies at lower prices, some truck buyers may not be willing to pay extra for an F-150 if gas prices are lower.

Considering that a Ford F-150 can already run to $40,000 without a lot of luxury options, there could be plenty of people in this second group.

Ford should be fine

Investors shouldn't start panicking about demand for the 2015 Ford F-150. Truck buyers are notoriously brand-loyal, so many current F-150 owners will upgrade to a new model even if having the most fuel-efficient truck is no longer a top priority. Ford's new aluminum body will also improve payload and towing capabilities, which are important features for truck buyers.

Still, on the margins, a lower fuel-price environment is likely to be better for GM as it spars with Ford for the No. 1 position in the U.S. truck market. Buyers new to the pickup market or with less brand loyalty will be more likely to buy a less fuel-efficient but cheaper GM (or Ram) truck if gas prices stay around $3 for an extended period of time.

No matter where gas prices end up, Ford is likely to sell 60,000 to 70,000 F-Series trucks each month once production of the 2015 Ford F-150 ramps up. However, higher gas prices may make it easier for Ford to reach -- or even exceed -- the high end of that range.