McLaughlin and Mostert were again 1-2 in practice.
Mika Hakkinen has acknowledged rumours linking his protege Valtteri Bottas with McLaren.
Weeks after the rumours first emerged, Ferrari has this week finally admitted that engine boss Luca Marmorini is leaving the Italian team.
Longtime Honda/Acura racer Peter Cunningham is behind the wheel.
Saturday's on track action features a pair of 10 minute long qualifying sessions ahead of twin 100km races.
The M-Sport team made a full repair and the popular Pole will restart under Rally 2 regulations tomorrow.
Sebastien Bourdais is coming off his first pole and first win since 2007.
The Australian duo will pair together starting next weekend at the Sepang International Circuit in Malaysia
Pietro Fittipaldi continues to go from strength to strength, extending his championship lead to 36 with 238 points.
Drivers include Bob Motz and his jet-powered semi.
No longer has to share space with Elan Motorsports Technologies.