Fernando Alonso laid down a marker for Ferrari by setting the fastest time so far in the year's first testing session in Valencia.
The Spaniard was 0.3 of a second quicker than world champion Sebastian Vettel in a Red Bull.
Scot Paul di Resta finished just over half a second behind Alonso in last year's Force India.
Lewis Hamilton made his first appearance in testing in the 2010 McLaren and finished fourth overall.