‘Jack,’ an L.A. hit, is out in N.Y.

Same format. Same owner. Different result.

CBS Radio confirmed Monday that WCBS-FM in New York City would drop the iPod-shuffle-style “Jack” format that it adopted two years ago and return on Thursday to the oldies format that the station had featured for more than three decades. WCBS had dropped from eighth to 16th in the local ratings during that period.

In Southern California, however, “Jack” continues to flourish on KCBS-FM (93.1), and there are no plans to change, General Manager Jeff Federman said. He said the station had finished No. 1 among English-language listeners in the 25-to-54 age range in seven of the eight Arbitron ratings since it adopted the format.