Hamilton, who topped the timesheets at both Thursday practice sessions, held only a small gap to teammate Valtteri Bottas in second place.
However after the second practice session, Hamilton had a gap of over seven-tenths of a second to Sebastian Vettel in third, with Mercedes appearing to be out of reach of its rivals.
"I don’t know where all the time has come from,” the five-time world champion admitted.
“But we’re constantly improving this car and understanding it and understanding the tyre. Those things come together and I guess that’s why you’re seeing the performance advantage we have."
Mercedes were expected to be the favourites heading into the weekend after its dominating start to the 2019 season, which has seen it take five one-two finishes.
Hamilton added that his crew have only been making minor tweaks to the car in order to improve the balance, and that he is pleased with the setup he has.
“I'm really quite happy with the set-up,” said Hamilton. “We’ve just been making small tweaks over the two sessions and even in the sessions making a couple of small tweaks.
“It’s a surprise to see the delta we had. I don’t know if maybe Max didn’t get his time or something like that.
“But the performance is fantastic, it’s incredible every year we come here we get this faster. And it’s that much faster you notice it when you’re going past the barriers and touching them you definitely notice you’re going quicker this year.”