George Russell says Mercedes "don't really understand" why they are now seemingly fighting amongst Ferrari and Red Bull at the front of the F1 field, after a productive Friday at the Miami Grand Prix.
The young Briton topped the timing sheets at the end of FP2, with teammate Lewis Hamilton just 0.2 seconds behind in P4.
Mercedes' impressive pace comes amid upgrades, with the team running a lighter front and rear wing for the season's fifth round, at a venue where the effects of porpoising appear to have reduced.
But practice means nothing, says Russell, who is keen to ensure Mercedes do not get carried away following their surprise unlocking of extra pace.
Russell and Mercedes to "go again" on Saturday
Russell described his team's Friday in Miami as their best of the season so far, with fans at the Hard Rock Stadium now licking their lips at the prospect of a six-car fight on Sunday.
When asked if it was too soon to get carried away with Mercedes' apparent improvements, Russell said: "Yeah, absolutely. We don't really understand why we've hit the ground running, to be honest.
"We always knew that this weekend the conditions should suit us better, as we've been struggling a lot with tyre warm-up, even in Bahrain, but this is the first real hot race of the season.
"For sure, it's going well, but we're not getting carried away. Practice means nothing, [and] we go again tomorrow."
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Porpoising still causing problems for Mercedes
Russell added that porpoising remains an issue, particularly on high fuel, but there are encouraging signs – at least on the Miami track.
"We know that it will always be there, but maybe it's working at a lower range compared to where we were previously," he commented.
"But yeah, for sure, in that high fuel run, I was feeling it, and it didn't seem to be any better. But if we can manage to do that with the car, lower to the ground, and obviously we seek the rewards...
"You generally have races that go in your favour, some races that go against you. Imola obviously wasn't a strong circuit for us, but so far, from what we see, the car is working well around Miami."
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