Max Verstappen topped the times for Red Bull in Saturday's hot, windswept and closely-contested final free practice ahead of Sunday's Bahrain Grand Prix.
In a session that was halted briefly after Frenchman Romain Grosjean crashed in his Haas-Ferrari car, the 19-year-old Dutchman clocked a best lap in one minute and 32.194 to finish one-tenth of a second clear of nearest rival Lewis Hamilton of Mercedes.
Sebastian Vettel, who shares the lead in this year's embryonic drivers' championship with Hamilton, was third fastest for Ferrari ahead of Valtteri Bottas in the second Mercedes.
Kimi Raikkonen was fifth in the second Ferrari ahead of Felipe Massa of Williams, Australian Daniel Riccirdo in the second Red Bull and German Nico Hulkenberg of Renault.
Carlos Sainz was ninth ahead of his Toro Rosso team-mate Russian Daniil Kvyat.
The top eight cars were separated by less than eight-tenths of a second in conditions that are not expected to be repeated in qualifying scheduled for later on Saturday as the sun, and the wind, goes down.
In marginally cooler conditions with an air temperature of 35 degrees Celsius and track of 39, the session began slowly. After early installation laps, Frenchman Esteban Ocon of Force India was briefly quickest before Spaniard Carlos Sainz planted his Red Bull on top of the times.
By the half-hour mark, both Ferrari and Mercedes were doing little bar check out their cars with slow uncompetitive laps as a strong wind arrived.
There was little for the fans, enduring the scorching sunshine, to enjoy before the session was halted by a red flag after 38 minutes when Frenchman Romain Grosjean spun and crashed at Turn Four, damaging the front of his Haas car.
In the severe heat, the tyres were over-heating and this caused a wild moment from Verstappen on his way to the quickest lap, at the time, of 1:33.249.
Three minutes later, after clearing up behind Grosjean's exclusion, Verstappen remained quickest ahead of Massa with 18 minutes remaining. Both Ferrari and Mercedes decided it was time to join the action.
Vettel ran wide on his first lap as Raikkonen, and then Bottas, clocked fastest laps before Hamilton, who had suggested on Friday that the 'daytime' sessions were pointless ahead of a floodlit race, came out.
Before the Englishman had a chance to go for a genuine quick lap, Vettel took over on top with a lap in 1:32.750 - just 0.004 seconds quicker than Bottas - to confirm that a tight qualifying scrap was in prospect.
The two-team battle was extended to three when Verstappen clocked his fastest lap with three minutes remaining before Hamilton secured second for the session, one-tenth adrift of the Dutchman, but nearly half a second clear of Vettel.