After tempers frayed between Honda and Mclaren, Honda made a deal with Toro Rosso to supply their engines for the 2018 season onwards. Many people believed this to be a stupid move for the team since they were changing from the Renault engine. However, the community quickly began to change their opinion after Gasly scored that incredible 4th place in Bahrain. People were now seeing that this power unit was considerably better than what they had seen in the back of the Mclaren for the past 3 years. Meanwhile, Mclaren was floundering around at the back of the grid with the Renault engine adding believability to the theory that the problems Mclaren suffered were of their own making, not Honda's. No longer were Honda engines the slowest in a straight line!
It wasn't all rosy for Toro Rosso though. During the 2018 season, they used a total of 8 engines across the 21 races. So what? Well, the number of engines allowed per season is 3. In comparison with all the other teams, including Mclaren Renault, Toro Rosso used double the amount of engine components which added up to A LOT of grid penalties. So while the engine was a step up from the previous years, it still was unreliable.
Engine components used during 2018 season
So what does Red Bull see that we don't? Clearly, they wouldn't blindly accept a deal with an engine supplier right? I personally see two reasons for the switch. One is that they were impressed with the development work they did with Toro Rosso and obviously think that, with a bit more development, the engine will close to the top. They will also have the advantage of being able to take and share data with the sister team which should hopefully aid them in their efforts to start winning championships again. The second reason for the switch, I believe, is that Renault flat out refused to supply them again. It's well known that relationships soured between Red Bull and Renault and the 2018 season didn't help matters(just look at Ricciardo's season) and with the frequent digs made by Horner adding fuel to the fire, it couldn't continue. Perhaps Red Bull was left with no option!
We can only wait until the lights go out on March the 17th to truly know if their decision will pay off. For Daniel Ricciardo, his move to Renault could be either the best or the worst decision of his career.