Hartley now has Toro Rosso F1 car he's been 'asking for all year'

Toro Rosso introduced a new front wing and floor, along with some minor bodywork tweaks, on Pierre Gasly's car in the United States last weekend but opted not to persevere with it because of limited dry running.

The update is on Hartley's car in Mexico, where Gasly has a grid penalty, and the New Zealander was extremely positive about its impact after lapping sixth-fastest in Friday practice.

"I'm really optimistic about this," he said. "In simulation it's really small numbers, we're talking half a tenth in terms of how much quicker.

"But the other side is the balance through the corners, and what it's meant to be giving us is what I've been asking for all season.

"Pierre and I have very different driving styles and what I require is very different.

"Sometimes it can hurt me and sometimes it can benefit me.

"This aero kit is in the direction of what I've been asking for all season.

"I'm excited from that point of view, there's a bit to be tested but today looks really promising.

"P6 seemed pretty genuine."

Hartley explained that he was excited about what the upgrade could do for him last week, even though he only ever saw the data on the sister car and heard feedback from his team-mate.

The 28-year-old's brief F1 career appears on the brink with ongoing speculation linking Nissan e.dams Formula E driver Alexander Albon to the second Toro Rosso seat.

Hartley's team boss Franz Tost also said on Friday in Mexico that his driver needed to do more to keep his drive.