Click here for full testing results from day four of the first F1 pre-season test at Circuit de Catalunya
Kimi Raikkonen has held on to top spot on the final day of the first F1 pre-season test at Circuit de Catalunya thanks to his morning blast on the new ultra-soft Pirelli tyres, while McLaren suffers a nightmare after Fernando Alonso was unable to set a timed lap due to an engine problem.
Raikkonen's timesheet topper of 1m 23.477s has ensured Ferrari takes the headlines at the opening test by claiming fastest time on three of the four days after Sebastian Vettel had been fastest on both days he drove the SF16-H.
Despite missing the three hours of afternoon running in the pits, Raikkonen comfortably held first place with his morning session lap while notching up 80 laps in total.
However, at the other end of the paddock it was a disastrous day for McLaren with Alonso's MP4-31 suffering a coolant leak after just three untimed laps. The problem confined the Spaniard to the pits for the rest of the day so he failed to set a time in what is effectively a quarter of his pre-season testing.
It also means more misery for McLaren who saw Jenson Button's running cut short yesterday afternoon with a separate engine issue.
Elsewhere, new team Haas stretched its VF16 to breaking point as Esteban Gutierrez was forced to stop on track at turn four with 70 minutes of action remaining. The Mexican had completed 89 laps before the incident with a fastest time of 1m 27.802s.
Rio Haryanto's debut with Manor Racing was also cut short when the Indonesian driver blotted his copybook again by spinning at turn four and smashing into the barriers. The damaged sustained to the rear of the car ruled out Manor for the final 90 minutes of track time.
While teams were making headlines for the right and wrong reasons, Mercedes quietly went about its business with another mammoth haul of mileage, topping its total distance covered over the four days to 5,000km.
Lewis Hamilton and Nico Rosbeg collectively notched up close to 190 laps on the final day with the majority of laps on the medium compound.
Elsewhere it was another positive day for Force India with the return of new development driver Alfonso Celis who ended the day third fastest with a 1m 24.840s on red super-soft tyres having completed 75 laps in total on day four.
Red Bull's Daniil Kvyat will be similarly upbeat by finishing the test second to Raikkonen but was unable to match the Ferrari for outright pace on the new ultra-soft Pirelli compounds in the morning session.
Renault's Kevin Magnussen has enjoyed another extensive day of testing in the RS16 having completed 153 laps on day four, almost double the amount team-mate Jolyon Palmer achieved on his two days combined, until his car gave up with 15 minutes of track time remaining.
Max Verstappen ran a low-key day in the new Ferrari-powered Toro Rosso notching up 110 laps with a best time of 1m 25.393s to put him fifth. Felipe Nasr paid a fond farewell to the 2015 Sauber with 121 laps in sixth on the timesheet.
Williams and Felipe Massa endured a difficult day after only completing 54 laps and ending the day a lowly ninth despite only using the medium and soft compound tyres.
However, any of Williams' frustrations will be multiplied at McLaren who after a bright start to the test now trail the rest of the field by a considerable margin both in lap time and mileage.