The Red Bull RB11 is a Formula One racing car designed by Adrian Newey for Infiniti Red Bull Racing to compete in the 2015 Formula One season. It was driven by Daniel Ricciardo and Daniil Kvyat. This was the last Red Bull car with engines badged as "Renault" and to feature their title sponsor Infiniti as they split from Red Bull at the end of the season due to a breakdown in the team's relationship with Renault.

The RB11 was launched on 1 February 2015. During pre-season testing, the car ran a camouflage livery – akin to pre-production cars – before the team reverted to their normal livery for the race season.

Red Bull had a terrible start to the 2015 Formula One season with a lack of performance from its Renault power unit compounded by reliability problems. Red Bull and Renault both stated that they seemed to have 'moved backwards' in performance terms from the previous year. After the first four races, Red Bull still continued to struggle for reliability and performance, only scoring 23 points, the team's worst start since the 2008 Formula One season. Red Bull faced more problems at the Bahrain Grand Prix, as Daniel Ricciardo's Renault V6 engine gave up as he exited the final corner on the last lap, thus forcing him to move onto his fourth power unit at the Spanish Grand Prix. Under the current regulations, drivers are permitted to use only four engines per season.

Renault countered with their own threat to pull out of Formula One as an engine supplier if its reputation continues to be damaged or is otherwise not profitable to the company. Red Bull had targeted the Spanish Grand Prix where it would make a step forward on performance due to multiple aerodynamic upgrades but in the end no results had come thus far as both drivers still finished a lap down on Mercedes and Ferrari. Renault quoted that past glories may have led to present woes with both Red Bull and Renault struggling with power unit reliability and aerodynamic upgrades. Ultimately, the team slumped to 4th place in the Constructors' Championship, with no wins for the first time since 2008. The team's best place was 2nd place each for Kvyat at Hungary and Ricciardo at Singapore on the tracks which suited more to the aerodynamics of the car rather than outright speed. Overall, the chassis proved to be at most on par with the dominant Mercedes team, but the engine proved to be a letdown to the car's performance.

...
Wikipedia