Red Bull Racing have dominated opening practice at the Hungaroring, with a 1-2 finish for Sebastian Vettel and Mark Webber. The defending world champion clocked 1:22.723 to finish ahead of his team mate's 1:22.982.
Lotus' Kimi Raikkonen and Ferrari's Fernando Alonso finished third and fourth, with the Spaniard's 1:23.099 only 0.012s faster than Romain Grosjean in the second Lotus.
McLaren's Jenson Button enjoyed a rare spell at the sharp end of the grid, posting 1:23.370 for sixth place. Force India-Mercedes' Adrian Sutil was seventh and Nico Rosberg was the fastest of the two Mercedes drivers, all the way down in eighth.
The German works team may be struggling to come to grips with the new Pirelli compounds, having missed out on the FIA-authorised testing session at Silverstone recently. Mercedes were banned from the test after having been found guilty of illegally testing Pirelli 2014 tyres at the start of the season.
The Italian tyre manufacturers tested revised 2013 compounds at Silverstone, alongside the traditional young drivers' test. Championship contenders Lotus, Red Bull and Ferrari were all present during the three days, potentially gaining a critical edge over Mercedes, in terms of how to adapt to the new and softer tyres.
Mercedes were given test data but that is not quite the same as first-hand information and certainly not quite as effective for their drivers - Rosberg and Lewis Hamilton. The British driver was particularly off the pace, with a 1:24.157 the fastest he could manage.
Opening Practice Review
The first practice session of the weekend began under bright sunshine and Toro Rosso's Daniel Ricciardo was the first man to emerge from the pits. Pirelli's medium tyres were the rubber of choice for the early installation laps; the Hungaroring is traditionally a very dusty track at the start of the race weekend, meaning the circuit needs to be cleaned and rubbered-in before faster lap times are set.
It took nearly 20 minutes for the first lap time to be set. Marussia reserve driver Rodolfo Gonzalez clocked 1:39.688. However, 10 minutes later Hamilton and Rosberg made their first appearances and McLaren's Sergio Perez followed, with the new benchmark - 1:25.476.
Raikkonen and Perez traded fastest times over the next few minutes but it was not till Alonso's first serious run that the times really began to fall. The Ferrari ace clocked 1:23.503 and beat that soon after, to head the sheet from Button.
An hour into the session and track temperature crossed the 40C mark, making life very uncomfortable for some drivers. Raikkonen was told of an airbox fire that was thankfully sorted out soon.
The Red Bulls left it extremely late for their first serious runs but it is a sign of their strong from that they only needed one shot to make it count. Webber beat Alonso to P1 just as Raikkonen nipped ahead of the Spaniard and the Vettel topped the sheets with a little under 30 minutes left.
There were no further changes to the top of the timesheets, with a number of drivers settling in to carry out set-up and tyre testing duties.
For details on the full timesheet and sector times, click here.