SPIELBERG, Austria, June 28 (Reuters) - Formula One leader Lewis Hamilton lapped fastest in first practice for the Austrian Grand Prix on Friday with Ferrari's Sebastian Vettel splitting the two Mercedes at the top of the timesheets.
Five-times world champion Hamilton set a best time of one minute 04.838 seconds at the sunny Spielberg circuit, 0.144 quicker than Vettel.
Hamilton's team mate Valtteri Bottas ended up third fastest, 0.017 slower than Vettel, with Mercedes carrying out a hurried engine change after discovering an oil leak about an hour before the start of the session.
Ferrari used the slower medium tyres, however, and were also running through a list of test items after a disappointing race in France last weekend while the Mercedes were on softs.
Hamilton has won the last four races, and six out of eight this season, and has a healthy 36 point lead over Bottas in the championship.
Bottas has been on pole in Austria, one of the shortest tracks on the calendar, for the past two years and needs another to give himself the best chance of reining in Hamilton.
Mercedes are favourites to take an 11th victory in a row this weekend, equalling the longest winning streak of the modern era that was set by McLaren in 1988, despite suffering a double retirement in Austria last year.
The session ended three minutes early with red flags after Renault's Nico Hulkenberg ran over a yellow 'sausage' kerb at the penultimate corner and ripped off half of the front wing, scattering debris across the track.
Ferrari's Charles Leclerc was fourth fastest with last year's winner Max Verstappen fifth for Red Bull at their home circuit. (Reporting by Alan Baldwin in London, editing by Christian Radnedge)