[14] At the end of the season, the car recorded a best finish of fifth place at the Hungarian Grand Prix,[15] and had scored just twenty-seven points, leaving McLaren ninth in the World Constructors' Championship.

This made 2015 the most difficult season in Formula One that the team had endured in 35 years, as a string of technical problems and retirements compromised the car's performance.

[18] Honda had previously competed in Formula One as a constructor when they purchased British American Racing in 2006, before selling the team to Brawn GP ahead of the 2009 season.

[21] The car was the first of the 2015 entries to pass its mandatory crash tests, getting final approval from the Fédération Internationale de l'Automobile (FIA) in December 2014.

The batteries housing the energy harvested by the MGU-H and MGU-K were merged with the Electronic Control Unit and positioned in front of the engine.

He further added that the car's performance issues could be traced back to a lack of outright power and poor fuel efficiency from the engine.

Despite being an average 13.3 km/h (8.3 mph) slower than the fastest driver through the speed trap over the first half of the season, an analysis of the engine's performance revealed that it had gradually reduced the deficit to the Renault Energy-F1 2015.

[37] The updates introduced in Belgium included changes to the combustion chamber, intake and exhaust aimed at reducing stress on other engine components to allow them to operate at peak efficiency.

Alonso's comments came amidst the first public signs of tension between McLaren and Honda with reports that the team had requested that Arai be removed from his position as Project Manager.

[46] Button was less optimistic, pointing out that the engine would struggle in Mexico as the high altitude of the Autódromo Hermanos Rodríguez—some 2,229 metres (7,313.0 ft) above sea level—would leave the turbine down on power given the low density of the air.

[47] Although the team's predictions of a difficult weekend were proven true after qualifying, they highlighted the deficit to the leading Mercedes through the less power-dependent sectors of the circuit as being consistently within three tenths of a second, the narrowest the margin had been over the course of the season.

[49] Fernando Alonso defended the move, suggesting that Honda's independent development programme would make it difficult for other manufacturers to copy the RA615H's design.

[50] McLaren CEO Ron Dennis took a broader view, attributing the team's difficult season to a range of factors—including chassis development and staff morale—rather than the engine performance alone.

[52] However, the team rejected the criticism, arguing that the infrastructure needed to establish such a partnership would distract from their own campaign,[53] and earmarking the 2017 season as the earliest possible date that an expansion could be considered.

[56] In the build-up to the Japanese Grand Prix, Alonso noted that although addressing the power unit's shortcomings remained the team's biggest challenge, he was unhappy with some of their trackside operations, citing a lack of running in Friday practice sessions, under-preparedness in starting procedures and pit stops, and unreliability of other parts—such as the gearbox—as compounding the problems with the engine.

[60] With Button qualifying thirteenth for the Russian Grand Prix, half a second behind the Red Bull of Daniil Kvyat, Brundle described the team as having made "their first meaningful progress of the season".

[61] However, three races later and following the upgrade introduced in Mexico, Brundle said that the engine was still down on power, inefficient, and lacking reliability and therefore suffering the same issues that had plagued it since the start of the season.

[67] However, Alonso and Button still qualified on the penultimate row of the grid ahead of the Manor Marussia drivers Roberto Merhi and Will Stevens.

[72] However, in the following races in Canada and Austria, the team's struggles came to a head as they were forced to reduce the power output of the engine to levels that had not been used since Australia, and could not therefore provide a competitive package for the long straights and slow corners of the Circuit Gilles Villeneuve and Red Bull Ring.

In addition, with their arrival in Austria, both Button and Alonso had used up their quota of engine components for the season, which combined with unscheduled gearbox changes, resulted in both drivers receiving twenty-five place grid penalties.

[77] The team only saw limited running as Alonso retired on the opening lap after a collision with Kimi Räikkönen, but they were able to assess the new design at a post-race test.

[78] With the Sporting Regulations amended to allow Honda to supply an extra engine without penalty,[79] McLaren opted to use it in Hungary, where the tight confines of the Hungaroring and lower demands on outright power were expected to benefit the MP4-30.

[86][N 3] The team reverted to the longer-specification snub nose for the Italian Grand Prix in order to provide better aerodynamic balance and lower drag on the high-speed Autodromo Nazionale Monza circuit.

For the Japanese Grand Prix, these pressures were raised by 2 psi (14 kPa) compared to the levels used during the 2014 race, which affected the MP4-30's ride height and vertical suspension travel and produced increased understeer.

In addition to the engine upgrades Honda brought to Russia,[42] the team sought to use the high-speed and low-degradation characteristics of the Sochi Autodrom circuit to test experimental bodywork parts, including the exhaust configuration.

[104] The team's struggles continued as the championship moved to Brazil for the penultimate round, with Alonso stopping twice on the circuit during free practice with a recurring engine fault that forced him to miss qualifying.

[106][107] Button later noted that the speed deficit of the RA615H around the Interlagos circuit relative to the other engines was "scary" despite Honda's extensive development programme.

[112] Alonso went on to finish seventeenth after receiving a drive-through penalty for his role in causing a collision with Pastor Maldonado and Felipe Nasr on the opening lap.

[122] The MP4-30 made one final appearance before being retired from competition, taking part in wet tyre tests at the Circuit Paul Ricard in preparation for the 2016 season.