Maybe Nick Gruber might consider crash-test dummy as his next career move. The troubled ex-boyfriend of Calvin Klein totaled current boyfriend John Luciano’s $100,000 BMW in a three-car accident in Los Angeles on Wednesday afternoon, reports The Post’s Kirsten Fleming. Even worse, Gruber was on a date with a woman when he had the crash. Luciano told us Gruber asked to borrow Luciano’s car to take his date to Six Flags Magic Mountain near LA. Gruber and the woman enjoyed the day at the theme park. But, Luciano said, on the way home, Gruber was broadsided by a PT Cruiser as he hung a left turn at Moorpark Street and Laurel Canyon Boulevard. The PT then smashed into another car and caught fire. The Beemer was wrecked, and Gruber went to Sherman Oaks Hospital after he suffered a broken nose and some bruises. None of the other passengers, including Gruber’s female date, was hurt. “The thing about Nick, he has a lead foot and rocks for brains,” Luciano quipped. Gruber sounded shaken but told us he was “alright.”