On 4 October, Detroit started the 7/2 second favourite in her attempt to win a second Prix de l'Arc de Triomphe and was ridden by Freddy Head, who had opted to ride her in preference to Gold River. Detroit was well-placed in the early stages but dropped away in the straight and finished twentieth of the twenty-four runners behind Gold River. On her only subsequent appearance, Detroit finished fifth behind April Run in the Turf Classic at Aqueduct Race Track. In 1980, Detroit was given a rating of 131 by the independent Timeform organisation, making her the highest-rated three-year-old filly of the year. She was also the top-rated three-year-old filly in the official International Classification, two pound ahead of Mrs Penny. Timeform awarded Detroit a rating of 126 in 1981. In the International Classification she was rated the second-best older female in Europe, seven pounds below Gold River. In their book, "A Century of Champions", based on the Timeform rating system, John Randall and Tony Morris rated Detroit an "inferior" winner of the Prix de l'Arc de Triomphe. Detroit was retired from racing to become a broodmare for her owner's Swettenham Stud. She produced at least twelve foals between 1983 and 2001:   Detroit died shortly after the birth of her last foal on 20 May 2001 at the Swettenham Stud.