SAKHIR, Bahrain -- George Russell topped the second day of this week's in-season test at the Bahrain International Circuit after switching from his regular team Williams to world champions Mercedes for the day.
The Williams race driver is under a Mercedes junior contract and was recalled to the championship leaders in order to drive one of the team's young driver days. His lap time in the Mercedes, which has won both grands prix this year, was 2.7s faster than his qualifying time in the Williams during the Bahrain Grand Prix last weekend.
At least two of the four in-season test days have to be completed by a driver with less than three grands prix experience, and until he starts the Chinese Grand Prix next weekend Russell still qualifies under the regulation. That means Mercedes could put a trusted driver in the car without using up one of its two race driver test days for the year.
Russell finished the day with 101 laps to his name, despite an engine change in the afternoon costing the team track time.
After Tuesday's freak rainstorm, which resulted in four hours of downtime, the teams enjoyed dry conditions throughout the day. Among the drivers keen to extend their mileage was Sebastian Vettel, who was back at the wheel of the Ferrari for the first time since his disastrous Bahrain Grand Prix. Vettel was not only slower than new teammate Charles Leclerc at the weekend, but also spun at Turn 4 while fighting for position with eventual race winner Lewis Hamilton. On Sunday evening he said he was keen to dedicate the day to getting his head around the handling issues affecting his Ferrari, and by the end of the session he had completed 103 laps with the third best time behind Racing Point's Sergio Perez in second.
After his debut with Ferrari drew huge attention on Tuesday, Mick Schumacher had a slightly quieter day at the wheel of the Alfa Romeo on Wednesday. It was always the plan to switch between cars over the two days and he got another 70 laps of F1 experience under his belt while setting the sixth fastest time.
The son of seven-time world champion Michael Schumacher was 0.012s slower than the time he set in the Ferrari, but given the gap in performance between the two cars the ultimate lap time was an improvement. Of more importance, however, was getting another day of F1 experience as the Ferrari Driver Academy assesses his potential to make the step from Formula 2 to F1 next year.
Schumacher's rival from last year's F3 championship, Dan Ticktum, made his F1 test debut in the Red Bull. The British driver, who will race in Super Formula in Japan this year, drove a 2011 Red Bull RB7 at a promotional day in Suzuka earlier this year, but Tuesday's test was his first drive in contemporary F1 machinery. He set the ninth fastest time by the end of the day with 135 laps.
Two-time world champion Fernando Alonso completed his brief return to F1 with another 69 laps of tyre testing. Alonso was drafted in by McLaren to give feedback on this year's car as well as work with tyre supplier Pirelli on next year's development tyres. Although the mileage was solid for an afternoon in the car, his best lap was unspectacular with the 11th fastest time. Comparing last year's McLaren to this year's, Alonso said the team had made a sizable improvement
"Well obviously it's a step forward in every aspect of the car," he said. "I think the car has more grip, the car is less draggy on the straights. The engine is a bigger step and better as well.
"Overall, as a package, I think the car is on the right direction. Obviously we saw in the first two races there is still another step to do if you want to compete with the top three teams, but as a first step I think, and hopefully consolidate as a fourth team or leading the midfield together with Haas, that's the target. I felt that on the car as well."
Elsewhere, F2 drivers Jack Aitken and Nicholas Latifi drove for Renault and Williams respectively, while Pietro Fittipaldi -- the grandson of two-time champion Emerson -- completed half of day of testing in the Haas.
Wednesday was the final day of this week's test, with teams now travelling to China for the next round of the season and Formula One's 1000th grand prix.
1. George Russell (Mercedes) - 1m29.029s - 101 laps (C5)
2. Sergio Perez (Racing Point) - 1m29.095s - 61 laps (C5)
3. Sebastian Vettel (Ferrari) - 1m29.319s - 103 laps (C3)
4. Carlos Sainz (McLaren) - 1m29.795s - 21 laps (C3)
5. Daniil Kvyat (Toro Rosso) - 1m29.911 - 110 laps (Dev)
6. Mick Schumacher (Alfa Romeo) - 1m29.998s - 70 laps (C5)
7. Alexander Albon (Toro Rosso) - 1m30.037s - 143 laps (C4)
8. Lance Stroll (Racing Point) - 1m30.049s - 35 laps (C5)
9. Dan Ticktum (Red Bull) - 1m30.856s - 135 laps (C4)
10. Romain Grosjean (Haas) - 1m30.903s - 87 laps (C4)
11. Fernando Alonso (McLaren) - 1:31.006 - 69 laps (Dev)
12. Pietro Fittipaldi (Haas) - 1m31.209s - 48 laps (C3)
13. Lando Norris (McLaren) - 1m31.303s - 72 laps (C2)
14. Jack Aitken (Renault) - 1m31.500s - 103 laps (C4)
15. Nicholas Latifi (Williams) - 1m32.198s - 100 laps (C4)