Sales of the 2015 F-150 are finally kicking into high gear. Image source: Ford Motor Company.

Come one, come all: It's the U.S. automotive industry sales day -- and it's shaping up to be another great month for auto investors. Ford Motor Company (F -3.01%) reported strong results early Monday morning and is setting up the company and its investors for an extremely profitable second half of 2015. Ford's July sales checked in with a 4.9% year-over-year increase, to more than 222,000 units sold.

"We continue seeing even stronger demand for our newest products, especially F-150, Explorer, Edge, Mustang and Transit," said Mark LaNeve, Ford vice president of U.S. Marketing, Sales and Service, in a press release. "With continued improvement in inventory, F-Series retail momentum continued building in July. Customers truly value the new F-150's capability, performance and fuel efficiency."

There were some very interesting figures in Ford's July sales results, so let's dig in.

Nice of you to join us
All year the story has been the same: Once F-Series production reaches full capacity, sales will begin to rebound. Finally, that forecast is coming to fruition in Ford's July sales results.

Ford's F-Series posted July sales of more than 66,000 units, nearly 5% higher than last year's July sales. Also, retail sales for the truck were up a staggering 13% for the month, which was its best July retail result since 2006. Furthermore, that jump in retail sales comes at a time when each F-Series is being sold for $3,200 higher than a year ago -- those are record-high average transaction prices for the truck, by the way.

While the 2015 F-150 is now being produced at full capacity, Ford has yet to fill its dealership inventories, which remain at about half the level of last year's at this time. As inventory begins to fill up, expect Ford to cash in on the delayed rental and fleet orders, which will send total sales higher throughout the remainder of 2015. Expect the 2015 F-150 to drive very strong profits during Ford's 2015 third and fourth quarters.

Ford's 2015 Mustang is selling very well in the U.S. Image source: Ford Motor Company.

The struggle is real
It's no secret that passenger car demand has taken a dive this year, and Ford's passenger cars are clearly not immune. Despite Ford's overall sales gain of 4.9%, the automaker's car segment checked in with a sales decline of 3.9% in July compared to last year. However, two vehicles bucked that downward sales trend: the Mustang and Fusion.

The Mustang has been a great story in 2015, with year-to-date sales surging 51% higher than last year's over the same time frame. In July the iconic muscle car checked in with a sales gain of 29% compared to last year, but perhaps the most interesting figure came from the vehicle's new EcoBoost engine take rate. On Ford's sales day conference call, executives noted that the Mustang's brand-new EcoBoost option represented 41% of Mustang sales nationally.

While Ford doesn't dish out as much engine take rate information as investors would like, this could be a very good sign for investors hoping to see the Mustang's sales reach 100,000 units in the U.S., which it hasn't achieved since 2007. All along I've said the new EcoBoost engine could reach an incremental car buyer who wouldn't have considered the Mustang before because of the lower fuel economy found in its larger engines. Now, with a more fuel-efficient option, the Mustang should find itself on many consumer car-buying lists it had previously been omitted from.

Ford's 2015 Lincoln MKC. Image source: Ford Motor Company.

Good or bad?
There's no question that Ford is putting its money where its mouth is with its Lincoln lineup. The company is going to pour $2.5 billion into four new models in an attempt to revive the struggling luxury brand. However, that payoff will be years down the road. So far in 2015 it's been difficult to understand whether the Lincoln story has been a positive or negative one.

One positive note in July was Lincoln's new MKX, which delivered a 27% increase in sales compared to last year and was being driven off dealership lots in just six days on average -- far faster than a rough industry average of 60 days. However, other storylines were a little more difficult to figure out.

For instance, Lincoln's year-to-date sales in the U.S. are up 8% to more than 56,000 units compared to last year, which sounds positive. However, when you back out the nearly 11,000 MKC sales that were generated this year during months when the vehicle wasn't available for sale last year, Lincoln's total sales are lower through July compared to last year -- suggesting that the MKC's incremental sales are propping up total Lincoln sales figures.

It's not necessarily a bad thing that the MKC is propping up Lincoln sales. But it does show that the rest of Lincoln's lineup has some work to do before the struggling brand's turnaround story gains momentum. Going forward, this is about the time last year when MKC's sales hit full speed, and monthly year-over-year comparisons will give a better idea of whether Lincoln's story is getting better or the brand is just spinning its wheels.

Ultimately, Ford posted some encouraging figures in July with some of its most important and profitable products. Investors should be very optimistic after a strong second quarter, and with more profitable third and fourth quarters forthcoming.