McLaren's Jenson Button was fastest in practice for the Spanish Grand Prix, edging Formula One points leader Sebastian Vettel of Red Bull in a slippery final session on Friday. Nico Rosberg of Mercedes, teammate Lewis Hamilton and Kimi Raikkonen of Lotus were the only other drivers within half a second of Button. A number of drivers ran off track as they grappled with tyres on the hot track, with Red Bull's Mark Webber of Australia and Williams' Bruno Senna performing the most dramatic spins.