Suzuki's Alex Rins led Yamaha rider Maverick Vinales by 0.057 seconds at the end of a tight second day of running at the Qatar MotoGP pre-season test.
Just as they did on Saturday night, Rins and Vinales traded session-best laptimes late in the session, with the former prevailing on this occasion with a lap of 1:54.593s.
Track action was minimal in the opening hour of the session, with KTM's Pol Espargaro setting the early pace with a 1:57.978s before being usurped by Ducati's Danilo Petrucci at the end of the first hour with a 1:56.247s.
Petrucci, who tried an aerodynamic device place at the rear of his GP19's bellypan, proceeded to improve to a 1:55.365s to go close to four tenths clear of Marc Marquez on the Honda.
Rins moved ahead of the Italian an hour later with an effort of 1:55.263s, though only briefly, as the works Ducatis once again made an assault on the top of the timesheet.
Andrea Dovizioso edged ahead by six hundredths, before Petrucci reassumed control with a brace of fastest laps – the second of which the first sub-1:55s lap of the test at 1:54.953s.
Setting that lap with just under three hours to go, it would be another 40 minutes before top spot changed hands, with Saturday's pacesetter Vinales guiding his Yamaha to a 1:54.781s.
Vinales improved to a 1:54.650s on an M1 fitted with a new seat unit, before Rins went marginally faster with a 1:54.593s on his GSX-RR as the session entered its final two hours.
Sepang Racing rookie Fabio Quartararo completed the top three on the satellite M1, with Petrucci heading Marquez – who tested the new Honda fairing debuted in Malaysia – to round out the top five.
Aleix Espargaro made it five manufacturers inside the top six on the Aprilia, 0.580s outside of Rins' time. LCR's Takaaki Nakagami slotted into seventh at the chequered flag on his 2018-spec RC213V.
Dovizioso spent Sunday's running comparing Ducati's 2018 aero fairing and the new one unveiled at Sepang two weeks ago. The Italian ended the day six tenths off the pace in eighth, with Cal Crutchlow [LCR] and KTM's Espargaro completing the top 10.
Jorge Lorenzo improved on his Saturday laptime by 1.4s with a 1:55.742s in Sunday's session, as he continues to adapt to the Honda after missing the Sepang test through injury.
Lorenzo was just 1.1s from Rins' time in 18th, with former team-mate Valentino Rossi – who has been fully focused on race pace – a tenth further back on the sister works Yamaha.
