Reserve driver Robert Kubica proved his worth by putting in a faster time than Sergey Sirotkin, who pipped the Pole to a Williams race seat, in his first official run out.
The Russian rookie was 0.327secs faster on day two of testing at a damp and chilly Circuit de Barcelona-Catalunya, where all 10 teams tested their new cars ahead of the 2018 season.
Kubica, who has only partial movement in his right arm as a result of injuries sustained in a rally accident in 2011, finished P7 from 39 laps compared to Sirotkin’s P8 from 52 laps.
Weather conditions have masked performances of all the cars but Kubica believes Grove-based Williams have “achieved the maximum we could”.
He was left encouraged by his first run-out: “It is not easy to jump into a new car with such difficult weather conditions and have the confidence to push, but I think we did some important work, although it was short.
“It gave us, and especially myself, an idea of how to work better for the future to address some areas where we can improve the car.”
The 33-year-old did, however, admit work needed to be done on ‘some issues’.
Lance Stroll took the Williams for a 46-lap stint without any problems on Monday.
But it was Renault who enjoyed the most satisfying opening day of testing.
The Enstone-based outfit impressed with Nico Hulkenberg fourth quickest before Carlos Sainz, in for the afternoon session, took the RS18 to 99 laps for the day.
Day two was even colder and Sainz, surprised to manage 65 laps, was in for both the morning and afternoon sessions, recording a P5 finish.
McLaren’s Fernando Alonso unexplainably lost his right rear wheel on Monday while for Banbury’s Haas, heavy drizzle towards the middle of the afternoon meant their first day rather fizzled out.
Romain Grosjean managed 55 laps before Kevin Magnussen hopped in the cockpit for a “difficult” 36 laps in Tuesday’s session.
Snow fall caused delays to the start of day three yesterday (Wednesday).
The second and final winter test, also to be held at Barcelona, will start on March 6. The lights go out for the new season in Melbourne on March 25.
n Williams have confirmed Martini will not extend its title sponsorship when it expires at the end of the season. Deputy team principal Claire Williams stressed the team is on a secure financial footing.