Two days after claiming a hugely impressive race victory at the Circuit de Catalunya to increase his championship lead to 17 points, Hamilton completed 151 laps in the W09 as Mercedes worked through their day one programme. They blistered very seriously and could have caused serious problems.
"This is more like it", said Hamilton on the slowing down lap after crossing the line a mammoth 20 seconds ahead of teammate Valtteri Bottas and almost half a minute ahead of fourth-placed Ferrari-rival Vettel.
Sebastian Vettel says he now understands Pirelli's decision to alter the tread depth of tyres for the Spanish GP, having suffered severe blistering when testing the normal compounds on Tuesday at the Circuit de Catalunya. On Wednesday he switched to the latest specification of the vehicle as part of a normal test day for McLaren and said he immediately noticed the difference between the two. There have been no weekends that I've been really way off the pace, like there was a few past year. I'm very interested to see what happens in Monaco next time out as they should be in better shape in qualifying.
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.
GP3 race victor Nikita Mazepin was fifth fastest in the Force India and completed 108 laps despite a auto issue in the morning. "We've had all the bosses here and there is not a single person in the team, or at least the hierarchy of the team, that has any concerns as far as I am aware".
"It's good to have the test to be able to compare", he said. 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 vehicle since the start of the year.
Spanish GP no reason to write off rest of F1 season
Isola also explained that giving all teams the opportunity to try out the different specifications in the test - something that was planned in advance of the weekend - was so that Pirelli could get a "proper comparison".
"Today, the auto and myself, I felt that synergy today, which I hadn't been feeling for the whole year", he said immediately after pulling up in parc ferme.
Toro Rosso chose to use two drivers on Wednesday with Sean Gelael behind the wheel in the morning before handing over to Pierre Gasly, who came ninth despite running just 39 laps. 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.
When the Briton came out, he was smack in the middle of the two Red Bulls, but beyond DRS range of Verstappen. "Race by race we're understanding the tyres more, which is a bit battle for everyone".
Force India's Nikita Mazepin earned fifth overall and set his best time on softs with just under 20 minutes remaining.
Paddy Power Betfair confirms talks with FanDuel
Earlier today, the company itself confirmed the rumoured deal , saying that it is now in merger talks with FanDuel . Deutsche Bank reiterated a "buy" rating on shares of Paddy Power Betfair in a research report on Friday, March 9th.