Belgian Grand Prix: Red Bulls fastest in second practice
Red Bull were surprise pacesetters in the second practice session at the Belgian Grand Prix at Spa-Francorchamps, as Mercedes ran their session in unusual fashion.
Max Verstappen set the pace - 0.2secs ahead of team-mate Daniel Ricciardo - as Mercedes' Nico Rosberg was only sixth and team-mate Lewis Hamilton down in 13th.
Mercedes did not run the fastest tyre - the super-soft - preferring to save their limited chosen allocation for Saturday.
Rosberg and Hamilton spent virtually the entire session doing race preparation work - especially important for the world champion, who will start from the back of the grid following a series of engine penalties.
Hamilton has used two entirely new power units so far this weekend as Mercedes take in one race the new parts he needs to complete the season following a series of failures in the early races.
Those problems meant Hamilton used too many turbos and MGU-Hs (the motor-generator unit that recovers energy from the turbo) in the first four grands prix and Mercedes needed to take more than the permitted five to get him through the season.
Making all the changes in one race weekend minimises the damage as no matter how many penalty places Hamilton receives, he can only be demoted as far as the back of the grid.
It is possible Mercedes may take a third brand new engine for Hamilton before final practice on Saturday morning to further improve his position.
Hamilton knows he is facing a "damage limitation" weekend and that Rosberg will almost certainly eat into his 19-point championship lead on Sunday.
Other drivers facing penalties
Hamilton is not the only driver who will drop to the back of the grid for this reason.
McLaren's Fernando Alonso will join him there after needing an engine change following a water leak in the first session.
The new engine fitted to Alonso's car is of the same upgraded specification as that of team-mate Jenson Button's, but the Briton did not hit any problems.
Button was ninth fastest, Alonso only 0.3secs adrift in 12th despite losing the entire first session.
Sauber's Marcus Ericsson also has an engine penalty, of 10 places.
It means the Swede, Hamilton and Alonso will be at the back in that order as things stand at the moment - although Hamilton would move to last place on the grid if Mercedes do fit a third engine on Saturday.
Impressive Red Bull
Red Bull's pace bodes well for a competitive performance this weekend - and delighted the thousands of Dutch fans who have come across the border to cheer on Verstappen in beautiful sunshine and temperatures of 31C.
But Mercedes almost certainly have enough pace in hand for Rosberg and Hamilton to qualify fastest.
This is underlined by the fact Rosberg set a time in the first session which was only 0.3secs off Verstappen's fastest of the day, on his first lap out of the pits and with the car fitted with the halo head protection system.
Mercedes have selected only four sets of the super-soft tyre for the weekend, and will need all those for qualifying day on Saturday.
The speed of Verstappen and Ricciardo is of greater concern to Ferrari, who had a difficult day and were struggling to beat the Force Indias.
Their fastest driver, Sebastian Vettel, was fourth fastest, 0.4secs behind Force India's Nico Hulkenberg. Team-mate Kimi Raikkonen was 0.2secs further back in seventh place and behind Sergio Perez, and the four-time champion was 0.9secs off the pace.
Ferrari's pace did little to diminish the sense of a team in crisis that has increasingly enveloped them this year as their performance has slumped, in addition to the departure of their highly regarded technical director James Allison last month.