Max Verstappen topped the first day of in-season testing at the Circuit de Catalunya as all ten teams returned to action for the first time since Sunday's Spanish Grand Prix.
Tuesday was one of four in-season test days scheduled for 2018, with a second day at Barcelona on Wednesday and a further two days after the Hungarian Grand Prix in August. The tests see a mix of experienced and junior drivers take to the track together as at least two of the four days for each team have to be completed by a driver with less than three grands prix to their name.
Verstappen's best time of 1:17.528 would have been good enough for seventh on Sunday's grid and was 0.7s slower than his qualifying time on Saturday. The lap was set on the hyper-soft tyre, which will make its race debut in Monaco and is the softest compound in Pirelli's range. It is not designed to be used on a track with as many high-speed corners as Barcelona, but teams will get some idea of how it will perform in Monte-Carlo in the twisty final sector of the Circuit de Catalunya.
Carlos Sainz also used the hyper-soft to set a time 0.034s off Verstappen and take second place in Tuesday's standings. The Renault driver's lap time was an improvement of a couple of tenths over his qualifying lap on Saturday and was 0.097s faster than Sebastian Vettel on the softs.
Vettel completed a number of medium length runs on the softs and mediums and returned to the pits with blistering on the surface of his tyres. Ferrari had hinted that Pirelli's decision to bring thinner tread tyres to Spain may have suited rivals Mercedes but judging by the condition of his tyres when he returned to the pits, the thicker tread would have resulted in the overheating Pirelli had feared and tried to avoid with thinner tread.
Romain Grosjean's hyper-soft lap from the morning session was still good enough for the fourth fastest time and he ended the day 0.921s off Verstappen. Nicholas Latifi was at the wheel of the Force India and, despite setting the fastest first sector towards the end of the day, finished fifth fastest on his hyper-soft run.
Following his win on Sunday, Hamilton was back behind the wheel of his Mercedes W09 on Tuesday. He completed 151 laps as the world champions tested a number of small updates and some new rear wing rain lights, which were being trialled for the FIA to determine whether they are more visible than the traditional single rain light in wet condition.
Stoffel Vandoorne was seventh fastest in the first of two McLarens on track on Tuesday. Formula 2 championship leader Lando Norris and test driver Oliver Turvery shared the second as they tested 2019 development tyres for Pirelli.
Antonio Giovinazzi was eighth fastest in the Sauber and caused the only red flag of the session when Sauber conducted a fuel run out test with 15 minutes left on the clock. He was 0.316s quicker than Oliver Rowland in the Williams, who finished ahead of Norris and Mercedes-backed F2 driver George Russel, who was testing 2019 tyres for Pirelli in a second Force India.
Sean Gelael was 12th fastest in the Toro Rosso ahead of Turvey, whose afternoon time rounded off the list of drivers.
Times at close
1. Verstappen, Red Bull, 1:17.528, 148 laps (Hyper-soft)
2. Sainz, Renault, 1:17.562, 119 laps (Hyper-soft)
3. Vettel, Ferrari, 1:17.659, 136 laps (Soft)
4. Grosjean, Haas, 1:18.449, 129 laps (Hyper-soft)
5. Latifi, Force India, 1:18.530, 107 laps (Hyper-soft)
6. Hamilton, Mercedes, 1:18.543, 151 laps (Medium)
7. Vandoorne, McLaren, 1:18.891, 85 laps (Super-soft)
8. Giovinazzi, Sauber, 1:19.693, 135 laps (Hyper-soft)
9. Rowland, Williams, 1:20.009, 121 laps (Hyper-soft)
10. Norris, McLaren, 1:20.997, 76 laps (Dev tyre)
11. Russell, Force India, 1:21.478, 123 laps (Dev tyre)
12. Gelael, Toro Rosso, 1:21.935, 50 laps (Hyper-soft)
13. Turvey, McLaren, 1:23.070, 58 laps (Soft)