The survey included 160 early buyers of the 2020 Sierra light-duty pickup with the 3.0-liter Duramax.
A survey last year found that 35 percent of all Sierra buyers were new to GMC, which shows the diesel option is conquesting at an even higher rate, Brook said.
One in five customers surveyed said they would brag to friends about how quiet the diesel engine is, and 96 percent said they were satisfied with the sound quality.
"The engineers have really done that for us," Brook told Automotive News. "They have produced an engine that is an absolute standout."
The Sierra will help redefine the image associated with diesel engines, he added, especially after reliability issues with GM's diesels of the 1970s and '80s led to class-action lawsuits and an arbitration program by the Federal Trade Commission with no time or mileage limits for buybacks.
GM went on to develop better diesel engines in Europe and Asia, but it kept the engines largely out of the U.S. market. The new GM turbodiesels, built in Flint, Mich., are the first the company has sold in light-duty pickups since 1997.
"The way people look at these has really, really changed. A diesel is nothing like it was five to 10 years ago," Brook said. "In the not-so-old days, you knew you were in a diesel. It was noisy, it was harsh. It didn't sound great. It didn't feel great."
The 3.0-liter Duramax is smoother, quieter and more fuel efficient than its predecessors, he said.
With a range of about 700 miles on a full tank, the diesel-powered Sierra could get drivers from Los Angeles to Salt Lake City or from Detroit to Michigan's Upper Peninsula and back without refueling.