Lewis Hamilton remained the quickest man in second practice ahead of Sunday's Chinese GP but only by the slenderest of margins in a very tight session.
The world champion improved on his morning best but did make a small mistake as he posted a best of 1:33.482s on the Ultrasoft tyre though it was just enough to lead Kimi Raikkonen's Ferrari by 0.007s.
Valtteri Bottas was a third of a tenth slower than in his teammate in P3 with Sebastian Vettel completing the top four just over a tenth slower than the British pacesetter.
Red Bull are also in the fight with Max Verstappen just 0.341s behind Hamilton in fifth though his teammate Daniel Ricciardo didn't set a representative time on the purple-striped tyre, ending the session a second down in ninth.
The battle in the midfield is just as close as at the front with a full second covering Nico Hulkenberg in sixth for Renault to Sergey Sirotkin in 16th in the Williams.
It is Renault and Haas that continue to lead, though Romain Grosjean would end the session down in 19th, that allowed Fernando Alonso to creep into the top 10 in P10 for McLaren.
Both Force Indias and Pierre Gasly were covered by less than a tenth in P11-13 with Stoffel Vandoorne, whose session was ended early by a loose wheel during his race simulation, and Brendon Hartley a few tenths further back.
Sirotkin led what is likely to be a continuation of the duel between Williams and Sauber at the back of the grid, though his teammate Lance Stroll would ruin his qualifying simulation with a high-speed spin in Turn 8, leaving him bottom of the timesheet.
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The second half of the session was given to long runs with the main question being how durable the Ultrasoft tyre would be.
Initial answers were variable with some struggling to make the compound last while Gasly managed 22 laps, just six short of what would be half distance so the strategies on Sunday are going to be very interesting indeed.
