Finnish driver Valtteri Bottas was fastest for Williams on the final day of pre-season testing in Barcelona as McLaren's reliability problems continued.
Bottas bettered teammate Felipe Massa's time from the previous day on the supersoft tyres, but was still some way off Mercedes' best on the slower soft tyres in Barcelona in 1 minute, 23.063 seconds.
Ferrari's Sebastian Vettel was second quickest when also running on the supersoft compound with Brazilian Felipe Nasr in third.
Nico Rosberg concentrated on mileage over speed for Mercedes as he completed a mammoth 148 laps in only the seventh fastest time.
However, the German's time of 1:22.792 from Friday remained the benchmark across eight days of testing at the Circuit de Catalunya.
By contrast, McLaren's inability to put their MP4-30 through its paces ahead of the opening Grand Prix of the season in Melbourne in two weeks' time continued.
Jenson Button could only muster 30 laps and was also way off the pace set by the leaders despite running on the soft tyres as was over two seconds behind Bottas.
Pastor Maldonado suffered a heavy crash early in the afternoon session to end Lotus' day early, but the Venezuelan was able to walk away unhurt.
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