Rossi was the fastest rider on both days of the opening test
Reigning world champion Valentino Rossi picked up where he left off as he set the pace in the first pre-season test.
The seven-time MotoGP champion lapped a wet Sepang circuit in two minutes, 00.925 seconds to head the field for Yamaha after two days of testing.
Australian Casey Stoner was 0.395 secs behind the Italian for Ducati with Rossi's team-mate Jorge Lorenzo, who completed 60 laps, third fastest.
The opening round of the 2010 season begins in Qatar on 11 April.
Dani Pedrosa knocked more than a second off the time he set on Thursday to record the fourth fastest lap on Friday for Honda.
Ben Spies was fifth on a Yamaha while Pedrosa's team-mate Andrea Dovizioso produced the sixth fastest time in Malaysia.
Colin Edwards (Yamaha), Nicky Hayden (Ducati), Aleix Espargaro (Pramac) and Loris Capirossi (Suzuki) filled out the top 10.
During the test, members of the manufacturers' association (MSMA) met to discuss proposals to change the bikes' engine capacity from 800cc to 1000cc in 2012.
Rossi has already said that a return to more powerful engine could persuade him to extend his career in MotoGP.
The 30-year-old Italian tested a Ferrari Formula 1 car for a sixth time over the winter and has not ruled out a future move to four-wheel racing.