"You will be surprised," he told reporters at the Circuit de catalunya after completing 105 laps. "It is really good. I can tell it will be quicker for sure."
The highly-rated driver, who took part in Friday practice for Renault at the Spanish Grand Prix, also said that he was excited to be driving the Mercedes on Wednesday.
The champions said instead that a race-experienced driver was needed to test new developments and turned to Wehrlein, the team's German reserve who has been placed with Mercedes-powered Manor this season.
Red Bull, who use Renault engines with Tag Heuer branding, won Sunday's Spanish Grand Prix in Barcelona while Mercedes drew a blank when Nico Rosberg and Lewis Hamilton collided and put themselves out of the race.
Wehrlein, 21, tested on Tuesday for Manor before handing the car over to the team's British development driver Jordan King.
Rosberg, the championship leader and winner of four of five races, tested on Tuesday and reigning champion Hamilton was not in Barcelona.
The decision means triple champion Hamilton will now not take part in any in-season testing this year as teams have only four days available each and two of them must be given to inexperienced young drivers.
Sunday's 18-year-old race winner Max Verstappen was also testing with Red Bull on Wednesday.
(Reporting by Alan Baldwin, editing by Sudipto Ganguly)
Share
