DETROIT – The return of the 4-cyl. car at Cadillac may not be too far off, General Manager Bryan Nesbitt suggests.

“Let’s ask the question,” Nesbitt tells Ward’s in an interview at the North American International Auto Show here. “Let’s find out.”

Cadillac’s last 4-cyl. model was the Cimarron, a Chevrolet-derived, entry-level compact badged with the Wreath & Crest between 1981 and 1988. The Cimarron is blamed for helping drag down Cadillac’s image, sending the brand into a tailspin from which it still has not fully recovered.

But at this week’s Detroit auto show, the marque takes a big step in downsizing with the XTS Platinum concept. The top-of-the-line 4-door sedan combines GM’s award-winning 3.6L V-6 with the auto maker’s next-generation 2-mode plug-in hybrid system.

Even by today’s standard for downsizing, where the U.S. trails the rest of the world, a 3.6L V-6 for a fullsize Cadillac is quite a jump down the displacement ladder. But to hear Nesbitt speak, perhaps Cadillac could have gone smaller.

“The question is, what is the (luxury customer’s) threshold,” Nesbitt offers. “This is a test well.

“It is understanding what they feel is tolerable or smart, and still in their mind a luxury proposition,” he adds. “Could you do a 2.0L twin-turbo? Could you boost a smaller powerplant? To me it makes a lot of sense, but will the customer be interested?”

Enter the ATS, a compact luxury offering Cadillac will target against the likes of the Mercedes-Benz C-Class and BMW 3-Series. GM confirms the car but offers no timetable, although it is widely expected within two years.

Nesbitt also plays the ATS’s potential powertrain combinations close the vest – Cadillac could go big, it could go small, he says coyly. But his description of what GM might offer with the ATS hints heavily at a 4-cyl.

“Ultimately, we are very interested in delivering something to the customer that is very agile, (with) very light and nimble driving dynamics,” he says, adding luxury customers are becoming increasingly oriented to downsized engines.

“It really is amazing to me, no matter who you talk to in the luxury segment, how interested they are in efficiency,” he says. “Yet, it’s not an economic value. They don’t look at it that way. It is the relevance of efficiency, making the smartest solution, and that’s what’s interesting.”