Team Abt's Edoardo has set the pace during the opening DTM practice at the Norisring as Audi dominate the early running with six RS 5's engulfing the top-ten order.
Mortara emerged as the quickest of all after posting a 48.878 second lap around the shortest venue on the DTM calendar.
In typical Norisring fashion, the Audi driver's time was just 0.057s better off than BMW's Marco Wittmann in second as only 0.162s was all that could cover the entire top-ten order.
Mattias Ekstrom, Nico Muller and Adrien Tambay completed the remainder of the top-five in third, fourth and fifth for Audi while championship leader Robert Wickens was the top Mercedes effort in sixth.
BMW's Tom Blomqvist found himself between an all Audi sandwich in eighth after separating the seventh and ninth placed Team Phoenix duo of Timo Scheider and Mike Rockenfeller.
Team HWA's Maximilian Goetz was the final runner to complete the top-ten in tenth for Mercedes.