Young Canadian hot-shoe Bruno Spengler ensured Mercedes topped the timesheets after Friday's second free practice at the EuroSpeedway, Lausitz, finishing the day marginally ahead of Hockenheim winner Bernd Schneider.
The best placed Audi runner was Mattias Ekstrom, the Swede headed first free practice, but had to settle for third in the second session in his Team Abt Sportsline machine. The next best-placed Audi proved to be Martin Tomczyk back in eighth.
Audi will be looking to the EuroSpeedway, a track where the Audi's traditionally go well, to wrestle the advantage from Mercedes who claimed the pole and the win in the season's first race at Hockenheim
Audi filled the first four slots on the timesheets in first practice, with Timo Scheider and Frank Stippler following Ekstrom in second and third with Tomczyk in fourth.
Britain's Jamie Green ended Friday's second practice in fifth, followed by fellow Mercedes drivers Jean Alesi and Mika Hakkinen respectively.
Green will look for a strong showing in Saturday's qualifying, buoyed by his pole position last time out at Hockenheim. Meanwhile, rookie Susie Stoddart ended practice at the bottom of the timesheets in her AutoScout24 Mercedes, however the Scot ended the first session in 18th ahead of Vanina Ickx and Olivier Tielemans.