Red Bull has sought clarification from the governing FIA after its engine was marked to be the sport's benchmark, not Mercedes.
Under F1's new regulations the FIA has a mechanism designed to keep the competitive field balanced -- since the start of the year it has been measuring the engine performance of all five manufacturers under what is known as Additional Development and Upgrade Opportunities (ADUO).
The FIA has not clarified exactly how it is measuring the engines, although all manufacturers agreed on the mechanism being in the regulations.
ADUO allowed them to declare a benchmark internal combustion engine (ICE) and then decide whether other manufacturers could be afforded upgrades this year and next through additional cost cap spend.
Ahead of the Monaco Grand Prix, teams and manufacturers were told Red Bull's ICE had been ranked ahead of the Mercedes engine, which is currently unbeaten across the season -- nothing official has been put out by the FIA yet, however.
The ranking means Mercedes, Ferrari, Honda and Audi will all be given additional cost cap spend for its engines for the next two seasons, while Red Bull will not.
Red Bull has queried that with the FIA in a bid to understand how the judgement was reached.
"We were all a little bit surprised with that news," Max Verstappen said. "Yeah, I guess that's why we're talking to the FIA now to see what happened there, how they came to that conclusion. There's not much more to say right now. That's what they're looking at."
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It remains unclear what timeline the FIA would work to if it reviewed the ADUO ranking as they stand.
When he was asked about it, Verstappen's teammate Isack Hadjar quipped: "I mean, I was checking if we won the first six races of the year, you know, and we didn't, so..."
It was not just Red Bull who were surprised by the FIA's engine judgement. Ferrari's Lewis Hamilton has talked about how much his team needs the ADUO boost, saying his team has the best aerodynamic package on the grid.
The seven-time world champion praised Red Bull for its engine project, which was started at the beginning of the decade under Christian Horner with the sole focus on racing in 2026.
"I mean it is definitely a surprise because Red Bull and Mercedes-Benz are very, very close," he said.
"Red Bull have done an amazing job with their engine but so has Mercedes-Benz. I heard that there were some people from Mercedes-Benz 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."