SUZUKA, Japan - Runaway leader Sebastian Vettel avoided a rash of spins and crashes Friday to clock 1min 33.852secs in the afternoon session, 0.168 quicker than team-mate Mark Webber, in hot conditions.
The performance was ominous from Vettel, who will win his fourth straight world title if Fernando Alonso finishes outside the top eight on Sunday.
The Ferrari man was 10th in the second session. Mercedes driver Nico Rosberg was third with Lotus's Kimi Raikkonen fourth.
"It's good to see we are up there today, but it's not always so important," Vettel said. "We need to step up our game for tomorrow, as Mercedes will be strong in qualifying."
But proceedings were overshadowed by news that Spain's Maria de Villota, 33, was found dead in a Seville hotel room a year after she lost her right eye in a serious accident in testing.
News of her death broke during the second session, prompting a flood of tributes from drivers and officials. De Villota had the accident while testing for Marussia last year.
"Today's news about Maria de Villota is horrendous and tragic," said McLaren's Jenson Button.
"She had been through so much - much more than most people will ever have to go through in their lives - and it's been so tough for her.
"This is a real shock to the whole Formula 1 'family' and the world of motorsport. My thoughts are with her family at this time."
Alonso, a compatriot of de Villota's, was given the news as soon as he removed his helmet after the second session.
"At the moment, I still can't believe it and need a while to stop and think about it. Of course, it's very sad news for the world of motorsport as Maria was loved by everyone," he said.
The news detracted attention from an incident-filled day of practice.
Sergio Perez, who suffered a hair-rising puncture at last weekend's Korean Grand Prix, skidded into a wall at high speed, leaving his McLaren badly dented and needing to ice down his right wrist after returning to the garage.
Alonso, one of many drivers who blasted tyre-makers Pirelli after Korea, spun at the tricky ninth turn, trashing his compound rubbers in the process.
Kimi Raikkonen lasted just two minutes on his medium tyre run, forced to abandon his Lotus after burying it deep in the gravel, but still posted the fourth-quickest time of the second practice.
Vettel then overtook pace-setter Alonso to get the Spaniard even hotter under the collar, with track temperatures nudging above 40C (104F).
Vettel has won the last four grands prix to open a 77-point lead with only 125 available from the last five races.
Lewis Hamilton had lapped quickest in the day's first free practice in 1:34.157, three tenths clear of Mercedes team-mate Rosberg, in another lively session which included the worrying sight of a wheel hurtling through the air.
Marussia's Jules Bianchi hit a wall heavily at turn nine, ruling him out of P2 due to chassis damage, before Pastor Maldonado's Williams lost a wheel coming through the 'Spoon' curve.
Maldonado's day came to a quick halt when, 12 minutes into the second run, he smashed into the same wall that did for Bianchi.