Mercedes' Valtteri Bottas finishes in-season test on top in Barcelona

BARCELONA, Spain -- Mercedes finished the second day of in-season testing at the top of the timesheets, capping off a successful few days at the Circuit de Catalunya in Spain.

After securing second place behind teammate Lewis Hamilton at Sunday's Spanish Grand Prix, Valtteri Bottas clocked the fastest time of the two-day test on Wednesday. His best lap was a 1:16.904 on super-softs, 0.7s slower than the time that secured him second on Sunday's grid, but was 0.068s faster than the next quickest driver on Wednesday, Antonio Giovinazzi in the Ferrari.

Despite feeling unwell in the morning with an upset stomach, Giovinazzi notched up 148 laps by the end of the day -- the most of any driver taking part in Wednesday's test. The Italian, who drove for Sauber on Tuesday and is Ferrari's third driver, used the hyper-soft tyre to set a 1:16.972 just before the lunch break

The pink-striped tyre is the softest in Pirelli's range and will make its race debut at the Monaco Grand Prix next week. It lasts for just over a lap at the Circuit de Catalunya but, underlining the differences in the two circuits, is expected to cover most of a race distance in Monaco where Formula One will race next.

F2 championship leader Lando Norris set the third fastest time on Wednesday with a last-minute quick lap on soft tyres in the McLaren. His lap would have secured 11th place on Sunday's grid, faster than regular driver Stoffel Vandoorne and 0.3s off Fernando Alonso's best effort on the super-soft in Q3. Norris' car stopped on track in the afternoon causing a red flag, but was soon back out once McLaren discovered a setting issue and rectified the problem.

It was the British driver's second day at the wheel of a MCL33 after completing a tyre test for Pirelli in a version of the car that was not running McLaren's latest upgrade on Tuesday. On Wednesday he switched to the latest specification of the car as part of a normal test day for McLaren and said he immediately noticed the difference between the two.

"There's definitely some differences," Norris said. "Positive I think in quite a few ways but there's still some things with the old one which are always positive, so it's trying to combine them and get both on one car which would make it even faster basically.

"I think in general it's a bit more downforce, it's good for me having the confidence to push at Turns 1, 2 and 3 and all the high-speed corners. I think overall it's definitely been a slight step forward."

Kevin Magnussen was fourth fastest in the Haas but stopped on track in the afternoon after his engineers spotted a problem in the car's data. The issue was notspecified by the team but brought an early end to Magnussen's running.

GP3 race winner Nikita Mazepin was fifth fastest in the Force India and completed 108 laps despite a car issue in the morning. It was his seventh appearance as a test driver for Force India after first testing for the team in July 2016. Asked if he would push for a further opportunity at the next in-season test after the Hungarian Grand Prix, Mazepin said: "Absolutely. I'm not pushing for that only, it's definitely my target and I'm always trying to deliver the best I can and be as professional as I can be."

Jack Aitken made his F1 debut in the Renault RS18 and completed 120 laps over the course of the day. Aitken is a Renault development driver and his test on Wednesday came three days after he secured his first F2 sprint race win of the season on Sunday.

Charles Leclerc was back behind the wheel of his Sauber on Wednesday and clocked the seventh fastest time ahead of Robert Kubica in the Williams. Kubica took on a Williams test role at the start of 2018 after missing out on a race drive, and prior to Wednesday's test had taken part in pre-season testing and first practice at the Spanish Grand Prix. His day at the wheel of the FW41 ended with 123 laps on the board as the team looked to better understand the issues it has faced with its car since the start of the year.

"The conclusions are that there will be a lot of things to watch, to analyse and double check," Kubica said. "There were quite a lot of things going on, with gathering data and trying to get on top of our issues.

"It was an interesting day from the driver's point of view, but I think it was even more interesting day from the aero point of view and for the guys at the factory to now have a look and see what we can get out of it."

Pierre Gasly took over from Sean Gelael in the Toro Rosso on Wednesday afternoon, setting a time 1.3s faster than the F2 driver who spent all of Tuesday and Wednesday morning at the wheel. Gasly was one place ahead of fellow F1 regular Vandoorne, who was driving a second McLaren dedicated to testing development tyres on a Pirelli-prescribed run plan.

Red Bull simulator driver Jake Dennis made his F1 debut in an RB14 on Wednesday. The British driver got a surprise call up to test the car this week, making a change from his usual Aston Martin GT car that he races in the Blancpain GT Series. Dennis finished the day ahead of Gelael in 12th and Nicholas Latifi in 13th, who was in a second Force India that was also dedicated to Pirelli tyre testing.

Times at close
1. Bottas, Mercedes, 1:16.904, 139 laps (Super-soft)
2. Giovinazzi, Ferrari, 1:16.972, 148 laps (Hyper-soft)
3. Norris, McLaren, 1:18.039, 79 laps (Soft)
4. Magnussen, Haas, 1:18.274, 75 laps (Hyper-soft)
5. Mazepin, Force India, 1:18.344, 112 laps (Hyper-soft)
6. Aitken, Renault, 1:18.942, 120 laps (Medium)
7. Leclerc, Sauber, 1:18.993, 139 laps (Hyper-soft)
8. Kubica, Williams, 1:19.253, 123 laps (Hyper-soft)
9. Gasly, Toro Rosso, 1:19.410, 38 laps (Medium)
10. Vandoorne, McLaren, 1:19.914, 96 laps (Development)
11. Dennis, Red Bull, 1:20.440, 74 laps (Medium)
12. Gelael, Toro Rosso, 1:20.763, 83 laps (Soft)
13. Latifi, Force India, 1:21.412, 121 laps (Development)