Edoardo Mortara topped a largely wet opening free practice session for this weekend's third DTM round of the season at the newly reopened Spielberg circuit in Austria.
The Italian's 1m26.780s lap came early in the session on a dry track and put the Rosberg Audi driver at the head of the time sheets by 0.129sec from the Persson Mercedes of Christian Vietoris. Heavy rain hit the track inside the first half-hour of the 90-minute session, and did not let up until much later on, rendering lap times meaningless.
Mortara's teammate Filipe Albuquerque and Mucke Mercedes man David Coulthard led Martin Tomczyk's Phoenix Audi as the top five was comprised entirely of older-spec machinery.
Zandvoort winner Mike Rockenfeller was the best of the drivers in a current-spec vehicle, the Abt Audi driver sixth, ahead of Maro Engel's Mucke Mercedes, Miguel Molina's older-spec Abt Audi and Renger van der Zande's Persson Mercedes.
Championship leader Bruno Spengler was only 16th quickest in his HWA Mercedes, four places behind his British teammate Gary Paffett, but two ahead of Jamie Green.