Kiwi Brendon Hartley produced a solid drive in his first day as a Formula 1 driver during practice for the US Grand Prix.

The Toro Rosso driver completed the second 90-minute practice session with the 17th fastest time after earlier being 14th fastest in practice 1. He was 3.319s slower than current championship leader Lewis Hamilton and 1.3s behind his teammate Daniil Kvyat.

The 27-year-old Hartley backed up his earlier run by posting times faster than both Sauber drivers and the Haas of Romain Grosjean.

The second session was dry and the Le Mans 24 Hour winner got plenty of time behind the wheel of his Toro Rosso using a combination of soft tyres and ultra softs as he got to grips with the car and how it adapted to a track he has plenty of experience on.

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Hamilton proved the fastest driver in both sessions in his Mercedes while Red Bull's Max Verstappen and Ferrari's Sebastian Vettel completed the top three.

Changeable conditions greeted drivers in the early session and all cars used the intermediate tyre while a dry line formed. The curbs were extremely slippery and caught a number of drivers out, who used too much of them.

Hartley had to pit early in the stint to fix teething issues with his helmet and seat but did post a faster time in the wet than his teammate. The Toro Rosso team opted to park the returning Kvyat for the first session of the weekend, allowing French youngster Sean Gelael to run the second car.

At the half hour mark the cross-over between intermediates and slicks was reached and Hartley set a series of impressive laps that were comparable to regulars in the mid-pack of the Formula 1 field on the ultra-soft tyre.

He was praised for his clear communication over the team radio and he handled the greasy conditions without error and posted the 14th fastest time of the 90 minute session.

The Palmerston North product was quicker than both Sauber cars as well as the Haas of Romain Grosjean although the weather rendered times largely irrelevant. He also set faster times than Red Bull's Daniel Ricciardo and Fernando Alonso's McLaren but those two drivers did not run during the driest part of the session.

The official timing on television displayed the Australian flag next to Hartley's name prompting a number of emails from upset Kiwis while the Sky Sport UK commentary team, led by Herald columnist David Croft, spent plenty of time talking through the differences between the two flags for the worldwide audience.

Hartley will incur a 30-place grid penalty for the race after his team changed the car's power unit before practice got underway. He will still take part in qualifying tomorrow but faces starting from the back of the pack although other drivers could face a similar penalty.