On 15 September 2017, it was announced that Toro Rosso would terminate Renault's remaining contract of customer engine partnership in order to sign the full-works Honda power unit partnership contract for 2018 onwards, after Honda had severed its ties with McLaren and thus Toro Rosso earned direct factory support from Honda as a flagship team. On the following day, the team confirmed that they would retain their final 2017 driver line-up into 2018, with Pierre Gasly and Brendon Hartley. During pre-season testing, many were surprised at the speed and reliability of the Honda engine, which had gained a poor reputation during the past three years with McLaren. However, the first race in Australia was unspectacular, with Gasly retiring with an engine failure after qualifying in last place and Hartley finishing 15th. The following race in Bahrain would be far more successful, with Gasly starting 5th and finishing 4th in what would eventually become the team's best result of the season, albeit with Hartley suffering an incident-strewn race and being classified 17th.