Sandy Huffaker / The New York TimesA row of Chevrolet Impala Limiteds, actually an older model of the Impala that is sold only to fleet buyers, on a National Car Rental lot in San Diego. If it feels as if your rental car is always a Chevrolet Impala, there’s a reason for that: 57 percent of all new Impalas sold in the U.S. last year became rental cars, according to data from Polk Automotive.

If it feels as if your rental car is always a Chevrolet Impala, there’s a reason for that.

Rental car companies registered 89,569 new Impalas during 2013, making it America’s top-selling rental car for two years running. Fifty-seven percent of all new Impalas sold in the United States last year became rental cars, according to data from Polk Automotive.

Some cars, such as the Nissan Altima and the Toyota Camry, are big sellers into the rental market because they are big sellers, period. But the Impala is one of 16 car and light truck models with 30 percent or more of their sales going to the rental market last year.

“National tries to address the issue of rental car roulette by just letting you pick your own car,” said Chris Ladd, a sales engineer who rents cars several times a month. “Unfortunately, what that means is you can pick absolutely any vehicle out of their vast collection of Chevy Impalas — even one of the fancier shades of gray.”

Ladd is being a little bit unfair: On Saturday at Ronald Reagan Washington National Airport, National had just a couple of Impalas to offer; the Chevrolet Malibu was the more prevalent full-size sedan. But he has hit on something here. Look at that lot, and the blandness is one of three themes that emerge in defining the vehicles that depend so heavily on the rental market.

Some were large SUVs and full-size vans, which users are disproportionately likely to want on a temporary basis. You might need a GMC Savana van for a few days, but you probably don’t want to own one.

Some were subcompact cars, like the Toyota Yaris, that don’t sell well in the U.S. market. Manufacturers keep these in their lineups because they sell well abroad; rental car companies buy them in the United States and offer them as deeply discounted rentals.

And some, like all those Impalas sold last year, were bland sedans nearing the end of their product cycle. You could call these models the honeydew melons of sedans, since the appeal of both lies more with the bulk buyers (of buffets or fleets) than with the individuals doing the eating or the driving.

Selling into rental car fleets has historically been seen as a low-margin business for the carmakers, so it’s no surprise that some of these models have been discontinued or heavily revamped. Chevrolet has shaken up the Impala.

“Let’s face it, it was a rental car,” Eric Ibara, director of residual value consulting for Kelley Blue Book, said of the 2013 Impala. “Starting in 2014, Chevrolet dramatically changed that. They redesigned the vehicle so that it was much more appealing to consumers.”

Ibara noted that the Impala’s residual value — a measure of a new car’s likely resale value in the used market — had improved markedly since the revamp, reflecting greater desirability. National Car Rental even partnered with Chevrolet to run a test-drive program in which customers could rent the redesigned 2014 Impala and then get another free weekend test drive rental when they got home.

But here’s the thing: Even after the revamp, the Impala is still mostly selling into the rental market. According to data from Kelley Blue Book, 74 percent of 2013 Impalas became rental cars; for the 2014 model year so far, the figure is still 54 percent. (The 57 percent figure at the top of this article is for the 2013 calendar year, so it includes a mix of model year 2013 and 2014 sales.)

The Impala continues to depend on the rental market in part because the old Impala lives on alongside the new Impala. It’s marketed as the Chevrolet Impala Limited, it costs a few thousand dollars less than the revamped Impala, and it’s sold only to fleet buyers like rental car companies.

GM has announced plans to keep making the Impala Limited at least through 2016, which means Ladd may not be getting away from what he calls “the Chevy Object” anytime soon.