By Ian Ransom
MELBOURNE (Reuters) - World champion Lewis Hamilton set the fastest final practice time for Mercedes ahead of Australian Grand Prix qualifying on Saturday as home favorite Daniel Ricciardo continued to have technical issues with his Red Bull.
World champion Hamilton clocked a quickest lap of one minute 27.867 seconds, opening a cavernous gap of nearly seven-tenths of a second over Ferrari's Sebastian Vettel.
Last year's championship runner-up Nico Rosberg, who led Hamilton in both practice sessions on Friday, was third fastest, almost a second behind his British team mate.
Ricciardo was unable to take part in the second free practice session due to an engine problem and faced further issues a day later, rolling back to the garage after stopping just outside the exit to pit-lane.
The Australian's best lap was 15th fastest.
Sauber were able to send two cars out in practice after former test driver Giedo van der Garde dropped his legal action against the team and refrained to claim his race seat at Albert Park.
However, Marcus Ericsson had a spin after over-steering into a kerb to finish 12th fastest, while his Brazilian team mate Felipe Nasr was 10th best.
Williams drivers Valtteri Bottas and Felipe Massa were fourth and fifth fastest respectively, with Ferrari's Kimi Raikkonen sixth.
McLaren underscored their lack of preparation for the new season with Kevin Magnussen 16th quickest and his team mate Jenson Button a further spot behind.
Manor Marussia, recently reborn after being taken into administration, were unable to put their cars on the track for a third successive practice session.
(Editing by John O'Brien)