During negotiations to secure a new supplier, Renault disclosed that they did not have the capacity to supply McLaren whilst meeting their commitments to customer teams Red Bull Racing and Scuderia Toro Rosso.

[5] In a departure from the last three seasons with McLaren, at pre-season testing in Barcelona, Honda showed significant progress with its power unit completing the second highest lap tally of 93 in the first day without any issue with Brendon Hartley at the helm.

[8] Following the close of testing, Hartley claimed the Honda PU was easier to drive and felt more powerful than the units supplied by Renault at the end of last season.

[10] Honda responded with a fix to the issue making note that both drivers were still using the flawed 2017 MGU-H as the brand new system they had developed for the 2018 power unit was not going to be ready in time for the first round.

[12] After making significant progress with the PU mapping during the practice sessions at Bahrain, Pierre Gasly managed a 6th place during qualifying which he was able to turn into a 4th-place result during the race.

[citation needed] However AMuS also reported that Honda had made great strides with the development of their Spec 3 PU with initial tests suggesting a power output of around 750 hp and that it may be ready for introduction at the Russian Grand Prix in Sochi, two race weekends earlier than planned.

Post-practice, Honda told media representatives the engine had provided more power than originally expected so early on; however this had a knock-on effect when paired to the STR gearbox in the car.