An upgrade package delivered at the Azerbaijan Grand Prix, the fourth round of the season, was the final development produced under Key's leadership.

Beginning with the Austrian Grand Prix, the ninth round of the championship, the new technical leadership delivered a significant upgrade package to the car, which began a marked improvement in the team's results.

The change in design direction has been praised as highly effective and successful to a degree not seen in modern Formula One and appeared to influence the development programs of several other teams.

[7] However, Key later revealed that the team had realised in September 2022 that the regulation changes to floor height would have an unavoidable negative impact on the car given its overall design philosophy, and began work on a new concept.

[8] In November 2022, Seidl stated he believed the team's struggles with the MCL36 would have an impact on the MCL60, namely that the lack of testing for the MCL36 and the time required to address its brake issues had delayed the start of development for the MCL60.

[9] Seidl, who was originally set to leave the team at the end of 2025 for the incoming Audi project, departed in mid-December 2022 to fill the vacancy at Sauber caused by the sudden exit of chief executive officer Frédéric Vasseur.

The MCL60 featured tighter sidepod geometry with a more aggressive undercut,[12][15] partly intended to free up space for ground effect inlet tunnels.

[18][19] Despite this, Stella said the team was "[n]ot entirely happy for the launch car" and intended to introduce substantial upgrades beginning in the fourth round of the season, the Azerbaijan Grand Prix.

[31][32] The car featured another special livery for the Singapore and Japanese Grands Prix, this time predominantly black with papaya orange highlights.

[37] The team reiterated during the pre-season test at Bahrain International Circuit that it was not satisfied with the launch specification car,[38] especially its excessive aerodynamic drag.

[44] The issue limited gearbox performance and forced Norris to pit every ten laps or so in order for the pneumatic pressure tank to be topped up.

[44] He finished seventeenth and last on track after completing six pit stops, motivated by McLaren's desire to collect additional data on car performance.

[52] At the Australian Grand Prix, McLaren ran a tighter circuit-specific engine cover and introduced new floor fences for the car's diffuser.

[58][59] The new floor involved a "radical" redistribution of aerodynamic load across the car's length, with particularly noticeable changes in the area ahead of the rear tyres.

However, the team had made a conscious choice to use all sets of softs allocated for Norris and prioritise starting position for the race, which precluded him from participating in the final session of the sprint shootout.

[64] In the Grand Prix, both drivers pitted immediately before a safety car, and were subsequently trapped in a DRS train until the closing stages of the race.

[72] Stella stated after the race that the results indicated McLaren needed to focus on developing the car's performance on low-grip surfaces, and in off-brakes, off-throttle periods.

[102] The result meant McLaren scored more points in the British Grand Prix than all the preceding races in the season combined, allowing them to take back fifth place in the WCC from Alpine.

[115] McLaren, who were expecting wet conditions, found that they had loaded the car with too much downforce for a dry race,[116] and Norris was running as low as seventeenth before recovering ten positions to finish in seventh.

[115] The car remained at the Circuit de Spa-Francorchamps after the Belgian Grand Prix to take part in a two-day test for Formula One's sole tyre supplier, Pirelli.

[122][123] Unpredictable wet conditions and poor strategy contributed to Norris finishing seventh and Piastri ninth,[124] with McLaren starting a review of strategic communication within the team as a result.

[126] The team introduced a range of new circuit-specific parts at the Italian Grand Prix, in an effort to avoid the issue encountered in Belgium caused by a lack of a low-drag aerodynamics kit.

[155] The Mexico City Grand Prix's high elevation and thus thinner atmosphere led McLaren to fit a circuit-specific engine cover and larger front brake ducts to the MCL60 to maintain efficient cooling.

[164] Although the floor and rear wing were repaired under the red flag, Piastri carried the winglet damage for the rest of the race, and he finished fourteenth.

[187] The team's mid-season upgrades were assessed as "one of the all-time great" turnarounds by Lawrence Barreto,[189] "one of the most impressive in-season development steps ever seen in F1" by Andrew Benson,[190] and a "miracle leap" by Hughes.

[189] Tony Dodgins of Motor Sport called the upgrade a "quantum leap", and said that the prospect of McLaren being the second fastest team on merit "could not have been entertained" at the first race in Bahrain.

Compared to the WDC- and WCC-winning Red Bull Racing RB19, the MCL60 had a significant straight-line speed deficit and continued to lack performance in long corners.

[194] After the Singapore Grand Prix, Hughes and Piola noted that McLaren's Austrian–British upgrades appeared to have inspired similar changes by Alfa Romeo to their C43, Alpine to their A523, and AlphaTauri to their AT04.

[201][202][203] Andreas Haupt of Auto Motor und Sport said that the car had developed "all-rounder qualities" and no longer substantially varied in performance across different circuits.

[204] After the season finale at the Abu Dhabi Grand Prix, Stella speculated that while the upgrades had improved pace, they may have worsened the car's handling, and said McLaren would investigate the possible consequences for the MCL38.