Both of the drivers trialled this engine at the previous Grand Prix in Russia, but Honda decided that further calibration checks were necessary and reverted to the old spec for the rest of the weekend.
Red Bull will no doubt be keeping a close eye on how effective this upgrade is, as they have made the decision to switch to Honda power next year in favour of Renault, ending its long-standing relationship with the French squad.
Hartley said: “We haven’t had an update for a long time. We did have an aero update which didn’t really work. We’ve definitely been waiting for an update on any description."
“I think the one from Honda is one that we're very excited about.We believe it will bring a good step in performance. I don’t want to say exactly how much but the truth is I don’t know the exact numbers. It’s a step that we’ll see on the lap time, which is important.”
Gasly added: “It’s a gain of performance, as I said in Sochi we don’t know exactly how much, it’s positive, we just needed to run a bit more with it to fine-tune it."
“It should give us more performance. I think in Sochi over one lap we looked better already and on Friday was quite positive, hopefully, similar here this weekend, after it’s going to be the first time we use it all race weekend. Clearly more optimistic in terms of performance I have been last few weekends.”
Bahrain International Circuit - Winter testing