"Jeep ads perform well, so the Chevy overperformance is especially meaningful because it's against an otherwise pretty strong brand," said Steve Shannon, strategic adviser for EDO.
A Fiat Chrysler Automobiles spokesman declined to comment.
A Chevy spokeswoman said these are among the brand's most effective ads. "They perform well on several key metrics — breakthrough, clarity of message, likability and, importantly, driving purchase intent," she said.
Chevy has run the year-end promotion since 2005, while FCA is new to the promotion as of Nov. 1, according to EDO.
"That was a game changer when Chevy launched that program," said Shannon, who was previously vice president of marketing for Hyundai Motor America and executive director of marketing for Cadillac. "I think they generated a tremendous amount of equity with it. While others have tried it, I think [Chevy] owns it."
Chevy's discounts, including an additional cash allowance, range from $12,260 on the 2019 Silverado 2500 LTZ crew cab to $3,436 on the 2020 Spark 2LT. Jeep's steepest discount is $6,185 off the 2019 Renegade Limited 4x4.
Before the campaign, Chevy was routinely fourth or fifth in EDO's rankings. A week after it started, it shot to the top.