"Do people want passenger cars? Yes," said Steven Center, vice president of the auto sales division for American Honda. "Forty-seven percent of our sales are passenger cars [at Honda], and we're picking up share in the passenger car segment — almost two points compared to the other mainstream brands," he said in an interview.

And it's not just the exit of the Detroit 3 — mostly — from the car market. "We're also gaining from other Asian brands too, such as Hyundai. So, I think it's kind of from everybody," Center said. "As the market shifts more to trucks, those people that prefer passenger cars are coming to us in droves. Almost 20 percent of the passenger cars sold in America are Hondas. That is crazy."

It helps that the Civic comes as a sedan, coupe and hatchback in normal, pocket-rocket and track-ready versions such as Type R hatch. It's the top U.S. vehicle for first-time buyers, millennials and multicultural shoppers. "Civic is just on fire. And when you consider it's at the farther end of its life cycle, to be achieving such sales volumes is absolutely incredible," Center said.

Jessica Caldwell, executive director of industry analysis at Edmunds, said the Civic is a prime example of a car that has evolved amid the changing auto industry. It has outlasted several of its rivals thanks to a formula that remains important to a significant chunk of the market that is looking for simple transportation, but not too simple.

"Civic has successfully endured the market shift toward SUVs because there is still a strong demand for cheaper, basic transportation at a price point below small SUVs. Civic fills this niche with a reliable brand name that has been a standout in the segment for decades," Caldwell said.

"Since price-sensitive car shoppers are less likely to take financial risks, Honda's reputation for longevity and quality makes Civic a safer prospect," she added. "The largest source of sales comes from prior customers, so with high quantities of Civics sold throughout the years, the buyer base is massive and is only going to expand as other brands shutter their car lines."

While it's noteworthy that Honda's incentives rose 16 percent last month from a year earlier according to ALG, they remain among the lowest in the industry and the automaker does not participate in fleet sales like most of its competitors.

Honda brand's average incentive this year, according to Motor Intelligence, is $1,898 per vehicle compared with $3,520 at Kia, $2,057 at Toyota and $1,540 at Subaru.

Center disputed that Honda's incentives were higher in August on a per-vehicle basis, and said they are lower this year overall.

"We're being much more efficient about how we spend the money," he said. "Some markets are APR markets and so we focus on [interest rates]. Some markets are lease markets. We focus on that. Midmonth we take a look at our sales progress, and then we turn a little dial." When needed, that dial can be turned to reduce supply rather than rejigger incentives.

Honda knew that August had the potential to be a big month and was ready with a marketing plan to take advantage of the sales climate. The end of summer is traditionally used to clear out inventory for the model-year changeover, and Honda wasn't the only brand posting double-digit percentage gains with the help of the Labor Day weekend.

"I think all the stars lined up right," Center said. "We had the supply, we had the message, we had the offers and we had the market."