After topping all four official MotoGP tests since leaving Suzuki at the end of 2016, Vinales started the new campaign in style, setting a best lap 0.596s clear of his closest challenger, Honda’s Marc Marquez.
Vinales moved to the top inside the first 15 minutes, turning a 1m55.668s to displace early leader Andrea Dovizioso (Ducati).
That benchmark stood into the final five minutes, with Marquez having become his closest challenger, 0.178s behind.
Jorge Lorenzo was the first rider to make a move in the closing stages, jumping up to second place and then replacing Vinales at the top with a 1m55.607s.
Ducati’s new recruit’s time at the top was fleeting, though, with Vinales responding immediately with a 1m54.739s, 0.868s faster than Lorenzo’s time, with Marquez also improving to move back into second place.
There was more to come from Vinales, as he went even quicker on his next lap to a 1m54.316s.
While reigning world champion Marquez also found more pace on his final flying lap, Vinales finished the first session of the year 0.596s clear.
Marquez’s Honda teammate Dani Pedrosa also flew late to claim third, ahead of Tech 3 Yamaha rookie Jonas Folger, while Lorenzo fell to fifth, 1.291s slower than Vinales.
Avintia Ducati’s Loris Baz jumped up to sixth at the very end, leading Cal Crutchlow (LCR Honda) and Johann Zarco on the second Tech 3 Yamaha.
Crutchlow’s session started with an apparent engine problem on the run to Turn 1 on his first flying lap, having to park his bike after it let out a plume of oil smoke.
The Briton rejoined the session on his spare bike, after changing his oil-soaked boots.
Valentino Rossi had to settle for ninth, 1.483s slower than Yamaha teammate Vinales, despite jumping up from 12th to sixth in the closing stages.
Aleix Espargaro was 10th for Aprilia, while rookie teammate Sam Lowes was the first rider to crash in the new season, 13 minutes in, the British rider losing his RS-GP at Turn 9.
Karel Abraham (Aspar Ducati) and Jack Miller (Marc VDS Honda) also crashed, separately at Turn 2 in the closing minutes, and were 15th and 17th fastest.
Dovizioso wound up 11th, having opted not to use a soft tire in the closing stages, ahead of Scott Redding (Pramac Ducati) and the best of the Suzukis, Andrea Iannone.
Pol Espargaro led the way for KTM in the Austrian manufacturer’s first weekend as a full-time MotoGP competitor.
Espargaro turned a 1m57.630s early the session, finishing 21st and 3.314s off the pace, with teammate Bradley Smith a further 0.484s adrift in 23rd and last.