Ducati's Jorge Lorenzo ended the final day of MotoGP testing at Sepang underneath the outright lap record on his GP18, as he recovered from a fall early in the session.
Conditions were perfect for the start of Tuesday's running, with the 3.4-mile Sepang circuit a hive of activity during the opening stages.
Repsol Honda's Dani Pedrosa was the early session leader with a 1:59.009s as the Spaniard – along with team-mate Marc Márquez – switched his focus to race simulations.
By midday, Pedrosa had been deposed by his compatriot Lorenzo, the Ducati rider guiding his GP18 to a fastest ever lap of the Malaysian circuit with a 1:58.830s, despite a small mistake at Turn 2.
Lorenzo – who crashed in the morning prior to his time attack – confidently stated after Monday's running that the 2018 Desmosedici was already better than last year's bike, though admitted there were still some small weak points to be ironed out.
Pedrosa's early effort kept him second on the timesheets, with LCR Honda's Cal Crutchlow just 0.043s adrift in third spot, ahead of the second factory Ducati of Andrea Dovizioso, who like his team-mate also suffered a small tumble early on.
Pramac's Jack Miller once again rounded out the top five as the Australian continues to adapt to the 2017 Desmosedici, while Suzuki's Alex Rins ended the day sixth having spent much of it evaluating the GSX-RR's much improved engine over a race distance.
Marc Márquez was half a second off the pace in seventh ahead of Valentino Rossi, with both factory Yamaha riders following most other teams in carrying out race runs. Team-mate Maverick Viñales was only 18th as a result.
Tech3's Johann Zarco tested Yamaha's new aero package, and after another day of extensive running on the '17-specification M1 chassis, the Frenchman is thought to be reverting to the frame he rode throughout last season.
Zarco clocked the ninth-fastest time on Tuesday ahead of Danilo Petrucci, with Avintia's Tito Rabat – who crashed twice – just 0.019s behind in an impressive 11th, as he continues to adjusts to the Ducati.
Andrea Iannone enjoyed a relatively trouble-free day following a brace of crashes and mechanical failures during the previous two days of testing. The Italian was 12th, ahead of Aprilia's Aleix Espargaro, top rookie Takaaki Nakagami on the LCR bike and Angel Nieto's Alvaro Bautista.
KTM's Pol Espargaro opted to sit out Tuesday's running after hurting his ankles in a 250km/h crash on Monday; test rider Mika Kallio was the top RC16 runner in 16th, with Bradley Smith 22nd.
