Lewis Hamilton fended off Kimi Raikkonen to claim the bragging rights over his rivals in both free practice sessions for the Chinese Grand Prix in Shanghai on Friday but the Finn's Ferrari showed enough pace to worry Mercedes.
Hamilton, who edged out team mate Nico Rosberg in the opening session, lapped the 5.451-km Shanghai International Circuit in one minute, 37.219 seconds in latter 90-minute run to shade Raikkonen by just four-tenths of a second.
"Generally the car was feeling good and it was nice to get the running and the preparations. Hopefully that will stand me in good stead," Hamilton told the BBC.
"The Ferraris look like they were as quick as they were in Malaysia, but hopefully we're quicker."
Daniel Ricciardo was a surprise third fastest in his Red Bull, the Australian leaping up the order late in the session after sitting out the opening 45 minutes as the team struggled to cool their brakes.
Ferrari's Sebastian Vettel, who won the Malaysian Grand Prix a fortnight ago, was fourth after surviving an early spin, edging out compatriot Rosberg, who made a mistake at the end of his fastest flying lap and could only manage fifth.
"On one lap, I think we'll be quickest and race pace we need to review now if we are looking okay or not," said Rosberg, who almost collided with Raikkonen late in the session as both cars jockeyed for position.
"That was definitely quite a tight one. He didn't leave much space in Turn Two, but okay, fair play, then I got him out in the next couple of corners. It was good racing and on Sunday, we might see some similar action."
In the morning session, Mercedes had appeared to have regained their dominant stride in the cooler Chinese weather after being dealt a shock defeat by Ferrari in the sweltering heat of Malaysia.
Hamilton was then more than a second faster than Vettel and Raikkonen but the Finn closed the gap in the second session when he fitted the quicker soft-compound tyres, finding more time than the Briton on the grippier rubber.
BRAKE FAILURE
Daniil Kvyat ended the day sixth-fastest but it was a far from smooth session for the Russian. Like Red Bull team mate Ricciardo, he sat out much of the afternoon and only managed 10 laps before being sidelined by a brake failure.
Both were driving with different brakes after struggling in Malaysia and had reverted many of the car's specifications to 2014 standards after a poor start to the season.
Valtteri Bottas ended a low-key day for Williams in seventh while Felipe Massa ended up down in 17th after finishing his session in spectacular fashion.
The Brazilian lost control under braking for the Turn 14 hairpin, lightly brushing the barrier before coming to a halt and prompting a brief red flag interruption.
McLaren built on an encouraging morning session with Jenson Button ending the day in the top 10. Fernando Alonso was 12th, with the team appearing to have made genuine progress after their early-season struggles.
There was a moment of drama early in the afternoon when a man believed to be a spectator darted across the start-finish straight as cars were speeding down it, crossing over safely into the pitlane before being apprehended by track officials.
