The wet weather of the morning session gave way to blazing sunshine for the second 45-minute outing of the weekend.
Pramac’s Jorge Martin set the initial pace on his Ducati at a 2m07.650s, though this was immediately bettered by Yamaha’s Fabio Quartararo.
The championship leader’s 2m07.529s didn’t keep him top of the pile for long, however, as COTA specialist Marc Marquez moved to the head of the timesheets with a 2m06.067s.
With just over 10 minutes of the session gone, Miller on the Ducati deposed Marquez with a 2m05.681s – though the Honda rider streaked half a second clear with a 2m05.156s.
Marquez’s advantage at the top of the standings was cut to 0.123 seconds by Miller, but the Honda rider still held sway as the session clicked into its final 10 minutes.
With uncertainty permeating the forecasts for Saturday, the closing stages of FP2 resembled a mock qualifying session as the field made their bids for a potential direct spot in Q2.
Marquez’s time was finally toppled by Ducati’s Francesco Bagnaia with a 2m04.793s – only for Takaaki Nakagami on the LCR Honda to instantly demote the Italian with a 2m04.612s.
Quartararo returned to the top of the pile with a 2m04.366s with just under three minutes remaining, but Marquez lit up the timing screens on his final flying lap.
Fabio Quartararo, Yamaha Factory Racing
Photo by: Gold and Goose / Motorsport Images
The Honda rider stretched two tenths clear of the Yamaha with a 2m04.164s, though he only narrowly held onto top spot in the end after a late effort from Miller put him 0.015s behind.
Quartararo held onto third spot ahead of the sister factory Honda of Pol Espargaro, who leaped up to fourth on his final lap.
He pushed Nakagami back to fifth ahead of Francesco Bagnaia on the Ducati, Martin and his Pramac team-mate Johann Zarco.
Alex Rins is currently the only Suzuki rider directly into Q2 having ended FP2 ninth with a 2m04.802s, while Avintia rookie Enea Bastianini jumped into 10th at the death.
Bastianini’s place inside the top 10 came at the expense of KTM’s Brad Binder, with the sister Avintia Ducati of Luca Marini shadowing him ahead of Mir on the other Suzuki.
Petronas SRT’s Andrea Dovizioso was sixth late on in FP2, but was shuffled back to 14th in the end ahead of the factory Yamaha of Franco Morbidelli, while Valentino Rossi was 17th on his SRT M1.
Late crashes at Turn 12 and Turn 18 for KTM’s Miguel Oliveira and Aprilia’s Aleix Espargaro proved hugely costly, as both ended up 19th and 20th, with Iker Lecuona last after a tumble from his Tech3 KTM.
Americas MotoGP FP2 results