Mercedes has won every grand prix so far in 2026 but the FIA determined that Red Bull has produced the best internal-combustion engine—an outcome the team is querying.ADUO—Additional Development and Upgrade Opportunities—was implemented into the 2026 technical regulations by Formula 1 and the FIA, in order to ensure one marque did not bake in a power advantage. ADUO is determined at three intervals per season—the staging of which was tweaked due to two grands prix not taking place in April—with a sliding scale of performance and financial allowances.The FIA has been monitoring the performance of the internal-combustion engine part of the new-for-2026 power units, and has formulated an ICE Performance Index.The ICE PI is calculated via a range of factors, including engine speed, MGU-K power, and a weighting to account for power sensitivity. Only the ICE part of the power unit is measured, not the ERS, and it accounts for 53 per-cent of the overall power output. Any power unit manufacturer whose ICE is at least two per cent behind the best performing ICE is granted ADUO. F1 Chinese Grand Prix 2026 - Sprint QualifyingADUO for a power unit manufacturer between two and four percent behind is granted one additional homologated upgrade in-season and one additional in 2027.That is increased to two for the respective timeframe for any PU manufacturer over four percent off the pace. There are also greater allowances in the cost cap, with those two to four percent behind getting another $3 million, those four to six behind getting $4.65 million more, and a further sliding scale up to 10 percent or more. It is believed that per the measuring system, the FIA has determined that Red Bull Ford Powertrains has the best ICE, with Mercedes between two and four percent behind, and therefore eligible for an upgrade this season and another in 2027.That is despite Red Bull taking a best result of third place, via Max Verstappen in Canada and Isack Hadjar in Monaco, this season. The other manufacturers—Ferrari, Audi, and Honda—were measured at over four percent off, making them eligible for the larger swathe of permitted upgrades. Mercedes’ engine is between two and four percent behind Red Bull’s and is therefore eligible for an upgrade this season and another in 2027.The measuring period concluded at last month’s Canadian Grand Prix, and were due to be made public within two weeks, but this has not yet happened as the FIA continues to verify the measurements. “I think we were all a little bit surprised with that news,” Verstappen said when he heard the ADUO outcome. “Yeah, I guess that’s why we were talking to the FIA. To see what happens there in terms of conclusions.”Teammate Hadjar cheekily quipped that “I mean, I was checking if we won the first six races of the year, you know, and we didn’t…” Ferrari has had a power shortfall so far in 2026, with its ADUO outcome unsurprising, but Lewis Hamilton nonetheless shared his surprise at Mercedes being granted development opportunities. “I mean it is definitely a surprise because Red Bull and Mercedes engines are very, very close,” Hamilton said. “Red Bull have done an amazing job with their engine but so has Mercedes. “I heard that there were some people from Mercedes that went to Red Bull, and either way, they’ve done something that no one thought they’d ever do in such a short space of time for a new engine manufacturer and fair play to them. I think Mercedes still has maybe as good an engine, it’s very, very close between them.”