DETROIT — Fiat Chrysler Automobiles and Wieden+Kennedy — the ad firm responsible for the “Imported from Detroit” Super Bowl ad with Eminem — are severing ties after a relationship that has lasted six years.

The creative partnership between FCA and the advertising firm resulted in many of the automaker’s most highly acclaimed marketing campaigns. Over the years, Portland, Ore.-based Wieden+Kennedy produced ads for Chrysler, Dodge, Jeep and Maserati.

Both the ad agency and the automaker said the decision to part ways was difficult, but necessary for reasons that were not explained.

“Making your mark in the automotive category isn’t easy. But we’re damn proud of the one we made with FCA,” Tom Blessington, managing director of Wieden+Kennedy Portland, said in a statement. “We’re even more proud of the company’s turnaround. Parting ways is always hard, but sometimes it’s just the right call. We wish FCA all the best.”

FCA Chief Marketing Officer Olivier Francois’ goal is for the automaker’s commercials to be both memorable and different. Wieden+Kennedy, Francois said, deserves credit for helping FCA achieve those goals.

“It has been a great partnership and, as these things do go, it is now the right time for both the agency and FCA to seek other pursuits,” Francois said in a news release.

The Super Bowl ad Wieden+Kennedy and FCA created with Eminem is widely viewed as groundbreaking and among the best that has ever aired during the Super Bowl.

In addition to the first-ever two-minute Super Bowl ad with Eminem, Wieden+Kennedy also produced a two-minute Super Bowl ad called “Halftime in America” with Clint Eastwood in 2012 and a 90-second ad for FCA’s Maserati brand called “Strike” for the 2014 Super Bowl.

Founded in 1982, Wieden+Kennedy, is an international advertising agency. Other current and former clients include AB InBev, Coca-Cola, Delta Air Lines, ESPN, Honda, Nike, Procter & Gamble and Verizon.