Mercedes has improved its F1 engine - but not with ADUO

Mercedes has ruled out using its Additional Development and Upgrade Opportunities token for the time being, with fresh Formula 1 engines introduced at last weekend's Austrian Grand Prix already delivering a "bit more spiciness" with performance.

The manufacturer's internal combustion engine has been deemed by the FIA to be at least 2% behind the benchmark Red Bull, which means Mercedes will be allowed extra spending and test bench hours to bring one new homologation this year and one in 2027.

While rivals Ferrari and Audi have already jumped on their ADUO allocations to introduce power unit upgrades, Mercedes has steered clear for now.

So while at the Red Bull Ring George Russell and Kimi Antonelli were given a host of fresh power unit components - including new internal combustion engines, turbo chargers, batteries and control electronics - none of these were actually upgrades.

However, it is understood that Mercedes did use the opportunity to introduce a raft of reliability tweaks across the board aimed at addressing concerns that had emerged in the opening part of the season.

And on the batteries, in particular, revisions to the control electronics were viewed as an essential step to help avoid repeats of what it thinks triggered the failures that put Russell out in Canada and Antonelli out at Barcelona.

The combination of reliability tweaks, which will have given Mercedes confidence to run the power units a bit more aggressively, plus gains that come from new engines that are not suffering from end-of-life degradation, were suggested by Mercedes team principal Toto Wolff to have given it a small power boost anyway.

So, despite the door being open for Mercedes to work on upgrades to further cement its championship domination, Wolff said it is happy to remain with what it has right now.

Asked to clarify whether the new power units included performance developments, Wolff said: "No, they were just new power units.

"With that comes less mileage, comes a little bit more spiciness. But there was no upgrade in it, and at the moment there's no upgrade planned."

Mercedes' decision to keep its engine in the same specification will be bad news for Red Bull, which will be unable to qualify for ADUO until one of its rivals has overtaken it by at least 2%.

The FIA will be reviewing the performance of all the power units for the period between the Monaco GP at the start of June and the Hungarian GP in late-July to see if there has been any shift in the rankings.

Red Bull is still trying to convince the FIA to change its mind on the original ranking from before last month's Canadian GP that put it on top, with a review of the data nearing its conclusion.

Laurent Mekies, Red Bull's team principal, expressed his fears of being put in a trap by rivals where, if they did not improve their internal combustion engines - the only part of the power unit taken into account in the ADUO ranking - then his outfit could be left unable to qualify for any upgrades.

Speaking in Austria about the dangers of getting snookered by others who have not made improvements, Mekies said: "You're right. There is a large risk there for Red Bull, so you are completely right in exposing that risk.

"It is one of the reasons why it is vital for Red Bull, and more generally for the sport, that we get that picture right.

"We are thankful to the FIA for the fact that they are taking the time to release their conclusion. And yes, you always would like to reach an earlier conclusion, but it's more important that we reach the right one, even if it takes a bit more time."

Beyond the Mercedes battery and control electronics changes that were introduced by its customer teams in Austria, fresh elements of the other power units components are expected to be phased in by them over the next few races.