It certainly is a bit of an eyebrow raiser - but then again, they struggled last winter and didn't have a terrible year.
Ericsson has just jumped above Hamilton in to fifth with a 1:25.758.
Hamilton has just re-joined the circuit, with Verstappen following closesly behind.
Verstappen improves to a 1:24.155.
@Tungath: No, but I would wager Hamilton is on a heavy fuel.
Hamilton's latest is a 1:23.633 - so maybe he's not on heavy fuel after all.
Button returns to the track.
That last time put Hamilton into second, just four tenths off Raikkonen.
@CJ: The sessions runs until 5pm local time.
Button has crawled to a halt at the end of the pit lane and is now being wheeled back into McLaren's garage. The team has just crept past the 50 lap mark.... for the entire test. Verstappen has completed that this morning.
Hamilton's pace has dropped slightly - into the 1:24s. Raikkonen is out there on hard tyres and immediately dips into a 1:22
Hamilton returns to the pits.
Grosjean joins Kimi on track and immediately posts a personal best in sectors one and two.
@MMimmyyo: Both are loaded with potential. It's hard to gauge where they stand after four days of testing but Sainz and Verstappen are very exciting talents.
Button is back out again.
Optimistic use of the phrase "more miles" from McLaren there. Only 5 laps to his name thus far.
Button lowers his benchmark to a 1:28.550 in his first timed lap in a long while.
Before all that, Grosjean lept into third with a 1:23.802.
Button posts a personal best on the final sector of his next lap but cannot improve overall.
@mfbull: It is. Unfortunately he missed the first day as Lotus did not show up in time, and Maldonado had been scheduled to run on Monday and Tuesday.
@Selva: I don't know why so many people think this is a genuine tactic in testing. Maybe towards the end of Barcelona, but as it stands these teams are testing their cars because they know little about them.
Button improves on his third attempt, however, lowering his best time to a 1:28.309. This is better from McLaren.
Button returns to the pit lane after a pleasing short run.
That just run for McLaren was six laps long. They're happy to accumulate the short mileage for the time being, it seems.
Ericsson and Grosjean still circulate as the unofficial lunch break period approaches.
I would wager that run will precede some longer runs this afternoon for McLaren.
The track falls silent as Ericsson and Grosjean return to the pits.
@Prithvi: The last we heard from the team it was struggling with an ERS issue.