Lewis Hamilton shot to the top of the timesheets in Friday's second practice for the Spanish GP while McLaren finished inside the top ten.
As within FP1, it was the Mercedes drivers who held the advantage in the early running. This time, though, it was Hamilton.
As the sun baked down on the Barcelona circuit with the track temperature up to 45'C at the start of the session, the Brit's 1:27.826 was 1.249s up on team-mate Nico Rosberg's best when the red flag was waved as Romain Grosjean's Lotus spewed debris down the front straight.
Putting in the laps, the engine cover of his E23 came loose and shattered, leaving debris everywhere.
The session was red flagged for three minutes as marshals swept it up.
Back into the action, the Ferraris were the first to swap from the hard to the medium tyres with Sebastian Vettel hitting the front on a 1:27.260 while Kimi Raikkonen was second, 0.520s down.
That changed when the Mercedes pairing made the swap.
Hamilton went quickest on a 1:26.852 while Rosberg only managed third place. The German, though, reported gearbox troubles, saying he was getting "rejected downshifts".
Vettel finished second, 0.408s down, while Raikkonen in fourth was the last driver to get within a second of Hamilton's P1 time.
The Finn later caused a few chuckles as, when working on long-distance pace, he told Ferrari he was getting "absolutely nothing out" of lapping the track again and again and again. The response; "understood" but keep doing it.
Daniil Kvyat was fifth ahead of Max Verstappen while Jenson Button recorded McLaren's best showing of this season as he finished seventh quickest.
One of the last to do their qualifying simulation, the Brit crossed the line with a 1:28.494, which put him 1.642s down.
Valtteri Bottas was eighth ahead of Carlos Sainz and Felipe Massa while Fernando Alonso almost made it two McLarens in the top ten as he clocked a 1:28.723. That, though, was only enough for P11.
It was still a great improvement from McLaren but there was more of the same over at Red Bull Racing as yet another engine problem meant Daniel Ricciardo's RB11 needed a new power unit. He ventured out late in the session to do four laps.
1 Lewis Hamilton Mercedes 1:26.852 27 laps
2 Sebastian Vettel Ferrari 1:27.260 0.408 37 laps
3 Nico Rosberg Mercedes 1:27.616 0.764 35 laps
4 Kimi Raikkonen Ferrari 1:27.780 0.928 37 laps
5 Daniil Kvyat Red Bull 1:27.943 1.091 25 laps
6 Max Verstappen Toro Rosso 1:28.017 1.165 32 laps
7 Jenson Button McLaren 1:28.494 1.642 32 laps
8 Valtteri Bottas Williams 1:28.525 1.673 39 laps
9 Carlos Sainz Toro Rosso 1:28.674 1.822 32 laps
10 Felipe Massa Williams 1:28.712 1.860 37 laps
11 Fernando Alonso McLaren 1:28.723 1.871 28 laps
12 Romain Grosjean Lotus 1:29.086 2.234 14 laps
13 Daniel Ricciardo Red Bull 1:29.098 2.246 4 laps
14 Pastor Maldonado Lotus 1:29.217 2.365 35 laps
15 Felipe Nasr Sauber 1:29.333 2.481 37 laps
16 Marcus Ericsson Sauber 1:29.361 2.509 34 laps
17 Nico Hulkenberg Force India 1:29.601 2.749 38 laps
18 Sergio Perez Force India 1:29.707 2.855 35 laps
19 Will Stevens Manor 1:31.929 5.077 30 laps
20 Roberto Merhi Manor 1:32.751 5.899 24 laps