The Gravity Charouz Mercedes team locked out the top two positions at the head of the times in free practice for this weekend's FIA GT Series encounter at Zandvoort.
Israeli Alon Day set the fastest time of the day in the second of the two 80-minute sessions at the Dutch track.
The former Indy Lights racer, who is sharing his Pro Cup Mercedes-Benz SLS AMG with Maximilian Buhk, ended up fastest on 1m39.575s, which put him less than one hundredth of a second up on teammate Sergei Afanasiev in the squad's Pro-Am entry.
The two Charouz Mercs had earlier ended up second and third in the opening session behind Laurens Vanthoor in the fastest of the three WRT Audi R8 LMS ultras. The Belgian driver's morning best of 1m39.695s was slightly quicker than fellow WRT driver Niki Mayr-Melnhof's third-place time in the afternoon.