Mercedes will receive the opportunity to make upgrades to their engine after the FIA adjudged Red Bull to have the strongest power unit in Formula 1 for the second time this season. Amid the introduction of new engine and chassis regulations this year, F1 implemented an Additional Development and Upgrade Opportunities (ADUO) system, which gives manufacturers with weaker power units the chance to catch-up to their rivals throughout the course of the season. In June, it was to some surprise that Red Bull – launching their first-ever in-house power unit this season alongside Ford – were announced as having the strongest engine, with the other manufacturers (Mercedes, Ferrari, Audi and Honda) all granted opportunities to update their power unit. Now, the second window has been disclosed and, once again, Red Bull have been announced as the most powerful engine manufacturer, with Mercedes in second (granting them one additional homologation) and Ferrari, Audi and Honda joint-third, granting them two additional homologations. While it is testament to the Red Bull-Ford Powertains team in Milton Keynes, it comes as a blow that Red Bull cannot look to upgrade their engine, given they currently languish fourth in the constructors’ standings, with star driver Max Verstappen sixth in the drivers’ table – 130 points off leader Kimi Antonelli, who drives for Mercedes. The FIA’s director of single seaters Nikolas Tombazis said: "The FIA has undertaken thorough and exhaustive analysis as part of our ADUO review process."With the release of the findings of period two, we are confident that, based on the quality of the data, its analysis is incredibly robust, giving us a high level of confidence in our findings.Max Verstappen's Red Bull team technically has the strongest engine (Getty)"We also have to respect the confidentiality and intellectual property of the teams and their Power Unit Manufacturers in disseminating any details from the findings."This is the first year of ADUO so naturally there are areas which we may evolve over time, in discussion with all the PU Manufacturers.”The second ADUO window concluded after the Hungarian Grand Prix prior to the summer break. The third ADUO period started after the Dutch Grand Prix and runs until the Mexican Grand Prix on 1 November. The next race is the Italian Grand Prix in Monza on 6 September.