Sainz was the busiest driver of the day, clocking up 127 laps across the eight hours of running.
His best of 1:29.348s left him 0.03s faster than Lewis Hamilton, who was in action in the morning session for Ferrari, and 0.08s quicker than Charles Leclerc who drove for the Scuderia later in the day.
In addition to his single lap pace, Sainz also worked through race simulations, as did a number of other teams, including practice pit stops.
The Spaniard was one of only two drivers to complete the full day’s running, the other being Liam Lawson at Red Bull.
It was an interrupted day for the Milton Keynes squad after a water pressure issue curtailed his running towards the end of the morning session.
Thought to relate to an all-new cooling system on the RB21, it limited his running to only 91 laps as he hands the car to Max Verstappen for Friday’s running.
Again it didn’t appear to be all smooth sailing at McLaren either.
Oscar Piastri only logged 44 laps before the lunch break, though Norris clocked 77 laps in the afternoon to leave the squad with 121 for the day.
That left the squad on par with rivals Ferrari (128 laps) while Mercedes managed 158 laps.
Some of the reduced running early in the day was a result of rain, which fell lightly for much of the morning but saw teams stay in the garage for a period approaching the second hour of the day’s action.
The rain did clear though skies remained overcast with temperatures – both track and ambient – largely stable across the day.
Teams return to the Bahrain International Circuit on Friday for the final day of F1 pre-season testing before teams head to Melbourne for the Australian Grand Prix on March 13-16.
Pre-Season Test: Day 2 Results
| Pos | Num | Driver | Team | Laps | Diff | Best |
| 1 | 55 | Carlos Sainz | Williams – Mercedes | 127 | 1:29.348s | |
| 2 | 44 | Lewis Hamilton | Ferrari | 45 | 0.031s | 1:29.379s |
| 3 | 16 | Charles Leclerc | Ferrari | 83 | 0.083s | 1:29.431s |
| 4 | 63 | George Russell | Mercedes | 71 | 0.430s | 1:29.778s |
| 5 | 12 | Kimi Antonelli | Mercedes | 87 | 0.436s | 1:29.784s |
| 6 | 18 | Lance Stroll | Aston Martin – Mercedes | 57 | 0.881s | 1:30.229s |
| 7 | 30 | Liam Lawson | Red Bull – Honda | 91 | 0.904s | 1:30.252s |
| 8 | 7 | Jack Doohan | Alpine – Renault | 80 | 1.020s | 1:30.368s |
| 9 | 10 | Pierre Gasly | Alpine – Renault | 40 | 1.082s | 1:30.430s |
| 10 | 6 | Isack Hadjar | Racing Bulls – Honda | 94 | 1.327s | 1:30.675s |
| 11 | 14 | Fernando Alonso | Aston Martin – Mercedes | 45 | 1.352s | 1:30.700s |
| 12 | 22 | Yuki Tsunoda | Racing Bulls – Honda | 46 | 1.445s | 1:30.793s |
| 13 | 81 | Oscar Piastri | McLaren – Mercedes | 44 | 1.473s | 1:30.821s |
| 14 | 4 | Lando Norris | McLaren – Mercedes | 77 | 1.534s | 1:30.882s |
| 15 | 5 | Gabriel Bortoleto | Sauber – Ferrari | 80 | 1.709s | 1:31.057s |
| 16 | 27 | Nico Hulkenberg | Sauber – Ferrari | 56 | 2.109s | 1:31.457s |
| 17 | 31 | Esteban Ocon | Haas – Ferrari | 69 | 3.723s | 1:33.071s |
| 18 | 87 | Oliver Bearman | Haas – Ferrari | 66 | 5.024s | 1:34.372s |
