While an increasing number of automotive analysts across the industry are growing wary of rising incentives and longer loan terms, one thing is for sure: New vehicle sales are accelerating. Both General Motors (NYSE:GM) and Fiat Chrysler Automobiles (NASDAQOTH:FIATY) are projecting the seasonally adjusted annualized sales rate, a term often used to measure the industry's health, to check in higher than 17 million for August -- something that hasn't happened in nearly a decade.

"August's industry sales results are looking even stronger than anticipated, which is a good sign for the industry," said Fred Diaz, Nissan's senior vice president for sales and marketing and U.S. operations, according to Automotive News. Despite a solid performance from the automotive industry as a whole, only one Detroit automaker boasted massive sales gains in August.

Jeep Grand Cherokee. Source: Fiat Chrysler Automobiles.

Fiat Chrysler Automobiles
In terms of sales volume, Detroit's third-largest automaker posted the most impressive year-over-year sales gains by a wide margin. Fiat Chrysler sold 198,379 units last month, which was a staggering 20% gain compared to last year. It was the automaker's best August sales performance since 2002, and it marked the 53rd consecutive month of year-over-year sales gains -- proving the company is on a serious hot streak.

Continuing the trend seen throughout 2014, Fiat Chrysler's Jeep brand is driving the automaker's sales higher. Jeep brand sales were up 49% last month, good enough to become the brand's best August sales performance in company history. While that sounds impressive, and it is impressive, it's not really unique, as Jeep has set a sales record in each individual month in 2014.

Also boosting the automaker's overall sales figures is the Ram pickup truck, which sold more than 43,000 units last month for a whopping 33% increase over last year's August total. Fiat Chrysler's Jeep and Ram brands are very much responsible for the automaker's overall 14% surge in new vehicle sales this year. Despite the company's sluggish Chrysler and Dodge brand sales, look for the automaker's overall sales to climb higher as consumers continue to drive full-size trucks and SUVs off dealer lots at a rapid pace.

2015 Mustang. Source: Ford Motor Company.

Ford Motor Company (NYSE:F)
While Ford certainly sold more vehicles than Fiat Chrysler, topping 222,000 units last month, its year-over-year sales gain of less than 1% leaves more to be desired. Part of the lackluster sales improvement was due to fleet sales declining 6%, although Ford's more profitable retail sales climbed 2%.

Ford's August sales gains might not impress, but the automaker's Fusion and Escape models continued to win over car buyers across the nation. Both the Fusion and Escape set records for year-to-date sales through August, and both are also on pace to break 300,000 sales for the full year. That's a feat only one other Ford vehicle has done in the last decade, America's best-selling F-Series pickup truck.

Speaking of the F-Series, which remains Ford's most profitable model by far, it managed to top 60,000 sales for the sixth consecutive month. For some additional perspective, Ford considers any month when the F-Series breaks 50,000 units sold a strong performance.

One thing for investors and car buyers to keep an eye on will be sales of the redesigned 2015 Mustang, which soon will be hitting dealerships near you. While the Mustang's new design is more evolutionary than revolutionary, the hype for the 2015 Pony car's 50th anniversary has been enormous. If early indications hold true, demand should be strong, which could send sales to heights not seen in more than a decade.

2015 Chevrolet Colorado. Source: General Motors.

General Motors
In terms of overall volume, General Motors reigned supreme over its Detroit competitors last month, with sales topping 272,000 units. Despite tallying the highest sales total, it also had the least impressive year-over-year sales result, with sales actually declining 1% in August.

General Motors also reversed Ford's sales-mix trend, with retail sales declining 4%, and fleet sales jumping 9% higher, compared to last year's August. Despite an overall decline in retail sales, the bright spot for GM in August was clearly its truck sales. GM's Chevrolet Silverado and GMC Sierra posted sales gains of 13% and 10%, respectively, compared to last year's August.

In other GM truck news, almost 28,000 orders have been placed for the Chevrolet Colorado, and nearly 14,000 orders for the GMC Canyon. GM's move to bring back its discontinued midsize trucks raised a few eyebrows at the time, as the segment has been in a drastic sales decline for years, but the risk could prove worthwhile if demand for a smaller truck returns. GM's risk in returning to the midsize segment could prove especially worthwhile, because Ford plans to keep its Ranger on the sidelines.

Bottom line
It appears that, with credit easily available and consumers willing to take longer loans, new vehicle sales and average transaction prices will continue to rise in the near term. That's good news for Detroit automakers, which have historically flourished when sales of SUVs, crossovers, and full-size trucks were robust.

Individually, you can expect these automakers' sales trends from August to continue throughout the remainder of 2014. Fresh designs of Jeep and Ram products will keep Fiat Chrysler's sales surging, new vehicle launches should help push Ford's sales up in the near future, and GM's sales remain a wild card, yet somewhat stable, during the aftermath of its enormous vehicle recall scandal.

Daniel Miller owns shares of Ford and General Motors. The Motley Fool recommends Ford and General Motors. The Motley Fool owns shares of Ford. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.