Pierre Gasly admits he still has some concerns over the reliability of Honda’s upgraded power units.

Gasly took a grid penalty at the last race in Canada after experiencing a problem with his first example of the new engine. Brendon Hartley suffered the same setback this weekend and will start from the back of the grid today.

“Reliability is still a bit of a question mark,” said Gasly. “But I’d rather have full beans and maximum performance and just go for the performance, on my side at the moment.

“In Canada I didn’t have any problem, we still need to do a lot of races with that engine so that’s why we decided to save the mileage on the Friday but hopefully we will be fast and be able to overtake like we did in Canada.”

However Gasly said Toro Rosso’s straight-line speed is also not as strong this weekend as it was in Canada.

“Just having a look at the GPS, in the corners we seem fine but just not so strong in the straight-line speed. And we need to have a deeper look, if we’re running too much downforce or if we could have done better.”

Gasly began the weekend using the old-specification engine before switching to the new unit on Saturday.

“I don’t know if it was more difficult to put the settings or… it’s a bit too early but we’re slower than in Canada in a straight line, compared to the others so we need to understand a bit better.

“Canada was really promising but in qualifying was the first time I ran with the new spec this weekend and it didn’t feel as good as in Canada,” he added. “I’m sure there are some explanations but at the moment we don’t really know but we struggled a bit more.”

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2018 F1 season