Raikkonen hit the front in the final hour of the afternoon, bolting on a set of Pirelli's yellow-marked soft tyres to set a time of 1m 30.665s. That was the fastest lap of the two days of running, and would also have been enough to secure the Finn third on the grid for last weekend's Grand Prix - two spots higher than he managed on the day.
"We've been doing our normal testing work, trying different things," Raikkonen explained. "We've tried to find good things. We always expect more as a team in terms of results. That's Ferrari: we want to win and keep working. We believe we can still win and we don't want to give up, but improve."
Esteban Ocon's morning benchmark was enough to keep him second, half a second down on Raikkonen. The Frenchman was also the day's busiest runner as he racked up 139 laps in Mercedes' F1 W07 Hybrid.
Red Bull junior Pierre Gasly, meanwhile, continued the team's strong recent form as he slotted into third, just ahead of Force India development driver Nikita Mazepin, for whom the two-day test represented a first ever taste of F1 machinery.
"These two days have been extremely useful and have no doubt been two of the biggest days of my life," said Mazepin, who set his fastest time on the supersoft tyre. "My main objective was to help the team out as much as possible and I’m pleased with how things went. We managed to test a lot of items and we also managed to do a few performance runs, which went very well."
McLaren, fastest on the opening day with Fernando Alonso, ended up fifth overall, with reserve driver Stoffel Vandoorne taking over from the Spaniard. As was the case on day one, the team broke through the 100-lap mark.
"We’ve had quite a successful day - a lot of aero stuff to do this morning and then after that I got some good runs in," Vandoorne said. "The car felt positive and I could push straight away, which is always a nice feeling."
Williams regular Valtteri Bottas was sixth fastest, with the team devoting part of the final hour to trialling its radical double-decker rear wing. The Finn ended the day nearly a full second clear of Haas rookie Santino Ferrucci - the American enjoying his second full day in the VF-16.
Renault's Jolyon Palmer was the day's other regular driver and the Briton wound up eighth overall, a few tenths down on Ferrucci.
Young drivers Sergio Sette Camara and Jordan King rounded out the top 10 for Toro Rosso and Manor respectively, while Pascal Wehrlein managed 128 laps but was the slowest of the day's runners as he focused on developing Pirelli's 2017 compounds in a 2014-spec Mercedes.
Sauber were the only team not present at the test.
Unofficial Wednesday test times from Great Britain
| POS | DRIVER | TEAM | BEST LAP | GAP | LAPS |
| 1 | Kimi Raikkonen | Ferrari | 1:30.665 | 103 | |
| 2 | Esteban Ocon | Mercedes | 1:31.212 | 0.547 | 139 |
| 3 | Pierre Gasly | Red Bull | 1:31.429 | 0.764 | 103 |
| 4 | Nikita Mazepin | Force India | 1:31.561 | 0.896 | 69 |
| 5 | Stoffel Vandoorne | McLaren | 1:31.764 | 1.099 | 114 |
| 6 | Valtteri Bottas | Williams | 1:32.423 | 1.758 | 98 |
| 7 | Santino Ferrucci | Haas | 1:33.141 | 2.476 | 107 |
| 8 | Jolyon Palmer | Renault | 1:33.308 | 2.643 | 98 |
| 9 | Sergio Sette Camara | Toro Rosso | 1:34.040 | 3.375 | 82 |
| 10 | Jordan King | Manor | 1:35.060 | 4.395 | 70 |
| 11 | Pascal Wehrlein (PIRELLI) | Mercedes * | 1:36.182 | 5.517 | 128 |
* 2014-spec car
