Pace shifted into a higher gear and lap times were slashed at the Circuit de Barcelona-Catalunya on Wednesday as teams ramped up their 2018 test programmes.
Several drivers dipped below the 2017 Spanish Grand Prix pole position time and the fastest driver of the day, Red Bull's Daniel Ricciardo, surpassed Felipe Massa's unofficial lap record from 2008.
The Mercedes-AMG F1 W09 EQ Power+ was put through its paces with another rigorous day of running, completing 175 laps of the track.
We once again split running between our two drivers over the course of the day, with Lewis Hamilton first on track and Valtteri Bottas taking over in the afternoon.
Lewis was first to climb aboard the W09 and take her for a spin bright and early on Wednesday, with the four-time World Champion taking on the morning shift in Spain.
He quickly got to work and spent a large chunk of the session at the top of the timesheets, before slipping to second place just before the lunch break. He remained there for the duration of the day.
The Brit put in 90 laps of the Circuit de Barcelona-Catalunya. His best lap of 1:18.400 on the Ultrasoft tyre was 0.749s quicker than his 2017 Spanish Grand Prix pole lap.
"Today has been positive," he explained. "The car is feeling good and the tyres are working. It's nice to have some good weather so we can really try and get in the mileage.
"The reliability has been good so far, which is a sign of all the great, hard work that the team has put in over the winter.
"It's still a work in progress, but it's definitely going in the right direction. The team's working hard - both here and back at the factory - to continue to climb the upwards gradient which we're currently on.
"I'm just so proud that I'm driving a creation that these guys have all worked to the bone to create. I'm proud to be the one who gets to go out there and try to exploit this car and bring them the results they deserve."
Valtteri jumped into the W09 for the afternoon running, continuing with Wednesday's main focus: aero tests and simulations.
He quickly moved into the top five on the leaderboard, eventually climbing to third with a 1:18.560 on the Ultrasofts. The Finn managed 85 laps during his time in the car.
A brief red flag before the end of the day caused the session to run a little longer than usual, in order for Valtteri and the other drivers to complete practice starts.
"The car felt OK," he said. "We did some shorter runs in the beginning, and then longer runs afterwards. We definitely made some improvements once again. We've made good progress since last year, but some other cars look quick as well.
"We had decent temperatures so we could do some proper testing and learned a lot from today. We have some work to do to get more out of the soft compounds.
"I always enjoy trying to extract everything out of the car. But we still haven't unlocked the full potential of the package we have, so there's more to come."
| Position | Driver | Team | Laps | Time |
| 1 | Daniel Ricciardo (3) | Red Bull | 165 | 1:18.047 |
| 2 | Lewis Hamilton (44) | Mercedes-AMG Petronas Motorsport | 90 | 1:18.400 |
| 3 | Valtteri Bottas (77) | Mercedes-AMG Petronas Motorsport | 85 | 1:18.560 |
| 4 | Sebastian Vettel (5) | Ferrari | 66 | 1:19.541 |
| 5 | Brendon Hartley (28) | Toro Rosso | 119 | 1:19.823 |
| 6 | Fernando Alonso (14) | McLaren | 57 | 1:19.856 |
| 7 | Carlos Sainz (55) | Renault | 88 | 1:20.042 |
| 8 | Romain Grosjean (8) | Haas | 78 | 1:20.237 |
| 9 | Kimi Räikkönen (7) | Ferrari | 49 | 1:20.242 |
| 10 | Lance Stroll (18) | Williams | 63 | 1:20.349 |
| 11 | Nico Hülkenberg (27) | Renault | 102 | 1:20.758 |
| 12 | Esteban Ocon (31) | Force India | 130 | 1:20.805 |
| 13 | Charles Leclerc (16) | Sauber | 160 | 1:20.918 |
| 14 | Sergey Sirotkin (35) | Williams | 80 | 1:22.350 |
