Grasser Lamborghini drivers Jeroen Bleekemolen and Hari Proczyk claimed a third consecutive Blancpain Sprint Series victory at Zandvoort in a race interrupted by heavy rain and two safety cars.
The qualifying race turned into a two-lap sprint to the chequered flag after the second of the safety car periods, Proczyk fending off the advances of Maximilian Gotz's HTP Motorsport Mercedes-Benz SLS AMG.
Proczyk crossed the line in his Grasser Racing Team Lamborghini Gallardo FLII just under half a second clear of the Mercedes Gotz shared with Maximilian Buhk.
"Hari did a great job - he and Maxi were much quicker than everyone else in the wet," said Bleekemolen.
"I hope it is not so exciting at the end tomorrow, because that was a bit too much."
Bleekemolen and Proczyk, who won both races at Brands Hatch in May, led all but one lap of the 60-minute race.
Local driver Bleekemolen, who had put the car on pole position, held a narrow lead from WRT Audi driver Laurens Vanthoor until rain started falling 10 laps into the race.
The Lamborghini driver was able to extend his lead to nearly seven seconds before the safety car came out just before the pitstop window opened.
Grasser sent Proczyk out in the lead, while the HTP Mercedes vaulted from fourth to second ahead of Stefan Rosina in the Reiter Lamborghini.
Proczyk was able to edge away from Gotz after the race went green and held a lead of 1.4s when the safety car was deployed again with 15 minutes to go after an incident involving Rosina and Filip Salaquarda's Scuderia Villorba Ferrari.
Gotz briefly put his Mercedes alongside the Lamborghini on the final lap but decided to settle for second ahead of tomorrow's full-points main race.
The Audi R8 LMS ultra Vanthoor shared with Cesar Ramos recovered to third after dropping to eighth courtesy of a slow pitstop.
Ramos was up to fourth before the final safety car and then passed team-mate Enzo Ide, who shared the second WRT Audi with Rene Rast, into the first corner when the race went green.
Fifth and sixth places were taken by two newcomers to the series: the Schubert BMW team claimed fifth with Dominik Baumann and Thomas Jager; and the Herberth Porsche squad sixth with Jaap van Lagen and Robert Renauer.
Results - 30 laps:
Pos Drivers Team/Car Time/Gap
1. Proczyk/Bleekemolen Grasser Lamborghini 1h01m45.733s
2. Buhk/Gotz HTP Mercedes +0.408s
3. Ramos/Vanthoor WRT Audi +2.245s
4. Ide/Rast WRT Audi +3.290s
5. Baumann/Jager Schubert BMW +5.263s
6. Renauer/van Lagen Herberth Porsche +5.480s
7. Lloyd/Pentus Bhaitech McLaren +15.331s
8. Landmann/Halek Grasser Lamborghini +20.376s
9. Rusinov/Ortelli G-Drive Audi +28.327s
10. Latif/Basseng Phoenix Audi +29.095s
11. Abril/Lisowski WRT Audi +1m27.882s
12. Stumpf/Brito Brazil BMW +1 lap
13. Pantano/Onidi Bhaitech McLaren +1 lap
14. Ebrahim/Toril Fortec Mercedes +1 lap
15. Colombo/Fumanelli ROAL BMW +1 lap
16. Rosina/Kox Reiter Lamborghini +8 laps
17. Salaquarda/Montermini Villorba Ferrari +8 laps
Mayr-Melnhof/Winkelhocke Phoenix Audi 12 laps
Dusseldorp/Afanasiev HTP Mercedes 12 laps
Jimenez/Bueno Brazil BMW 4 laps