The Manor driver, who also acts as Mercedes reserve, is a late replacement for fellow Silver Arrows youngster Esteban Ocon, who was scheduled to be behind the wheel of the F1 W07 Hybrid on Wednesday, having driven for Renault on the opening day in his role as the team’s third driver.
It is understood Mercedes - who had Nico Rosberg in the car on Tuesday - made the switch on the basis that they wanted an experienced driver to test new components.
However, their decision to run Wehrlein, who completed 86 laps for Manor on Tuesday, means that neither Rosberg nor Lewis Hamilton will be able to take part in the second of this years in-season tests at Silverstone in July as Mercedes will be obligated to run young drivers.
The rules state that teams must dedicate two of the four in-season test days exclusively to young drivers who have not competed in more than two Grands Prix.
You can follow minute-by-minute timing updates on the official F1 App - go to 'Results and Standings' and click 'Test'.
