On his opening day of pre-season testing Nico Hulkenberg has topped the morning session while Ferrari missed the opening three hours of track action with a fuel flow issue on Kim Raikkonen's car.
With the majority of teams opting for long stints of aerodynamic work, data logging and baseline set-up the fastest lap chart became a secondary concern as teams stuck to the medium Pirelli tyres. Hulkenberg therefore rose to the top with a 1m 25.286s midway through the morning session in the VJM09, while Renault's new driver Kevin Magnussen jumped to second albeit using the yellow-band soft compounds.
However, Ferrari lost over three hours in the morning after discovering a fuelling problem with Raikkonen's SF16-H. As a result the Finn could only produce a handful of laps in the final 50 minutes of the session.
After a whole host of driver switches from day three Nico Rosberg was the only one to return after Mercedes switched its testing plan with the German in the W07 in the morning before handing over to Lewis Hamilton this afternoon. Rosberg ended the session third overall with a fastest lap of 1m 26.084s.
Carlos Sainz enjoyed a productive morning with 66 laps under his belt despite a brief pause after he pulled up at pit exit. The Toro Rosso driver had been practicing race pit stops and sprinted off before his right rear wheel gun mechanic had secured the tyre, forcing the team to halt Sainz on track.
After a quick recovery under a red flag Sainz returned to end the morning fourth quickest ahead of Daniel Kvyat's opening morning in the Red Bull-TAG-Heuer combination.
Felipe Massa had a quiet morning period notching up the mileage on his first day of 2016 pre-season testing for Williams and ended the session narrowly ahead of fellow Brazilian Felipe Nasr in the 2015 Sauber.
Jenson Button continued lengthy aero work in the McLaren-Honda in eight overall while Grosjean also piled on the laps with a quick half century.
F1 debutant Rio Haryanto had an eventful maiden session after a small delay to the morning he spun out at turn five in the final half an hour, beaching his Manor Racing car in the sand. That caused the second red flag stop of the day to enable the Manor to be planted on the recovery vehicle and back for the lunch break.