The McLaren MP4-30 was a Formula One racing car designed by Tim Goss and Neil Oatley for McLaren to compete in the 2015 Formula One season. The car was driven by 2005 and 2006 World Drivers' Champion Fernando Alonso, who returned to McLaren eight years after he last drove for the team and 2009 World Champion Jenson Button.Kevin Magnussen, who drove for the team in 2014, temporarily stood in for Alonso after a test accident. Additional testing and development work was carried out by Magnussen, Stoffel Vandoorne and Oliver Turvey. The car was the first built by McLaren since the MP4/7A—which contested the 1992 season—to be powered by a Honda engine, known as the RA615H, after McLaren ended their twenty-year partnership with Mercedes at the end of the 2014 season.

The car was nicknamed the "size zero Formula One car" by the team for its distinct sharply tapered rear end, which was achieved by designing the Honda engine to operate at higher temperatures than other engines. At the end of the season, the car recorded a best finish of fifth place at the Hungarian Grand Prix, and had scored just twenty-seven points, leaving McLaren ninth in the World Constructors' Championship. Button and Alonso were classified in sixteenth and seventeenth positions respectively, in the World Drivers' Championship, while Magnussen was not formally classified, as he did not start the one race that he entered. This made 2015 the most difficult season in Formula One that the team had endured in thirty-five years, as a string of technical problems and retirements compromised the car's performance. An analysis of the project pointed towards failure in communication between McLaren and Honda, Honda under-estimating the technology required for the engine, and critical faults in the engine's design, as the cause of the team's problems.

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