Between the Racing Lines 🏁| Formula 1 is complicated, confusing and constantly evolving. This story is part of our guide to help any fan — regardless of how long they’ve watched F1 or how they discovered it — navigate the pinnacle of motorsport.In 2026, one of the biggest changes to Formula 1’s technical regulations in the championship’s history focused on overhauling the engines, bringing significantly more electrical power into the mix.This has received intense criticism, and discussions about the balance between engines’ electrical energy and internal-combustion power for the 2027 season are ongoing. But the proposed changes, if agreed upon and formally approved, would center on altering engine hardware to ensure drivers can push flat-out for longer.But there is an existing development mechanism, ADUO, aimed at fostering closer competition among engine constructors. This has long been part of the rules for the 2026 season.ADUO stands for Additional Development and Upgrade Opportunities, and means that any engine manufacturer judged to be off the pace of the leading engine — currently that of Mercedes — can improve its design. At the same time, development opportunities for the leader are limited.There are review periods for this to occur repeatedly throughout the season, and different levels of upgrades are permitted. These are calculated based on how a manufacturer’s internal combustion engine part performs at set points in the year.Mercedes nailed its engine ahead of the 2026 season and has enjoyed a run of dominance across the opening races, with victories in all six grands prix held so far. The squad known as the Silver Arrows made a similar leap to the front of the pecking order the previous time F1’s engine rules changed, in 2014.The difference now is that the ADUO system has been introduced to boost the chances of Mercedes’ rivals quickly catching up, which they took years to do after 2014. The big question is whether they can now get on good terms with the leader.“I think it’s going to be very difficult,” Ferrari driver Charles Leclerc said at the 2026 Canadian GP in late May. “(Mercedes) has a very big advantage.“I think it will definitely help to try and get closer. Whether it will be enough to close the gap, I don’t know.”Here’s everything you need to know about ADUO.What is ADUO?In the weeks leading up to March 1, all five F1 engine manufacturers worked to homologate their power units. These are Mercedes, Ferrari, Red Bull Powertrains, Honda and Audi.