Craig Fagan crossed for Caleb Folan to score an unusual header in the first half, before Lewis Alessandra equalised for the Latics in the second.
City's next game is the penultimate friendly of pre-season, away to Hearts on Sunday (kick-off 2pm). The match is being shown live on Setanta Sports.
City line-up: Matt Duke, Bernard Mendy (Richard Garcia, 78 mins), Michael Turner, Anthony Gardner (Wayne Brown, 59 mins), Andy Dawson; Craig Fagan, Ian Ashbee, George Boateng, Péter Halmosi; Geovanni, Caleb Folan.
Un-used subs: Boaz Myhill, Liam Cooper, Sam Ricketts, Dean Marney, Nick Barmby, Dean Windass.