Barcelona - Sebastian Vettel topped the early times on the fourth day of the second testing session in Barcelona on Friday.
The Ferrari driver clocked 1min 22.765sec to lead the time sheets with Mercedes world champion Lewis Hamilton sitting fourth.
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Hamilton is due to be replaced by teammate Nico Rosberg for the afternoon session.
Manor's rookie driver Rio Haryanto was unable to put in any laps due to mechanical issues with his Mercedes-powered MRT05 car.
Sebastian Vettel (GER/Ferrari) 1:23.852 (54 laps), Carlos Sainz Jr (ESP/Toro Rosso) 1:23.134 (57), Sergio Perez (MEX/Force India) 1:23.721 (44), Lewis Hamilton (GBR/Mercedes) 1:24.133 (69), Daniel Ricciardo (AUS/Red Bull) 1:24.427 (61), Jenson Button (GBR/McLaren) 1:24.714 (56), Jolyon Palmer (GBR/Renault) 1:24.859 (31), Marcus Ericsson (SWE/Sauber) 1:25.031 (57), Romain Grosjean (FRA/Haas) 1:25.255 (53), Felipe Massa (BRA/Williams) 1:25.696 (63)