MONZA, Italy, Sept 4 (Reuters) - Formula One world champion Lewis Hamilton set the pace in first practice for the Italian Grand Prix on Friday with Mercedes team mate and closest rival Nico Rosberg nearly half a second slower.
The Briton, who will be chasing his 11th pole position in 12 races on Saturday, told reporters on arriving at Monza with his hair dyed blond that he was going through an 'experimental' phase.
There was nothing radically different in his track performance, with the championship leader picking up where he left off in Belgium two weeks ago with a fastest time of one minute 24.670 seconds.
On a sunny morning in the former royal park outside Milan, Rosberg -- 28 points behind Hamilton in the championship with eight races remaining -- was 0.463 seconds slower with the Mercedes pair again in a class of their own.
The champions have brought an upgraded engine to Monza, the fastest track on the calendar, and it showed with rivals trailing far behind.
Ferrari's Sebastian Vettel, preparing for his first Italian race in the home team's red overalls, was third quickest -- but a massive 1.588 slower than Hamilton -- while team mate Kimi Raikkonen was sixth.
The usual array of Ferrari banners in the stands, several of them supporting stricken favourite Michael Schumacher and others paying tribute to the late Jules Bianchi, testified to the enduring passion of the local fans.
Germany's Nico Hulkenberg was fourth on the time sheets despite a fuel leak that prompted him to tell his Force India team over the radio: "I have a wet bum, it smells like petrol".
Mexican team mate Sergio Perez was fifth fastest.
The session was halted briefly when Spaniard Carlos Sainz lost control of his Toro Rosso at Parabolica and skidded into the gravel, bringing out the red flags at the half hour mark.
Honda-powered McLaren, who will collect more grid penalties with both Fernando Alonso and Jenson Button, endured another difficult session with the Spaniard 17th and the Briton 18th.
Both stopped early for engine changes. (Reporting by Alan Baldwin; Editing by Julian Linden)