Nico Rosberg beat Mercedes team-mate and title rival Lewis Hamilton to set the pace in first practice at the Brazilian Grand Prix.
The German was 0.221 seconds quicker than Hamilton and nearly a second clear of the field, which was led by Toro Rosso's Daniil Kvyat in third place.
During the session news broke that the Marussia team has ceased trading.
Toro Rosso's Max Verstappen, who is making his grand prix debut next year at the age of 17, was sixth.
The impressive Dutchman was as high as third at one point in what was his third outing in practice in preparation for next season.
Ferrari's Fernando Alonso was fourth ahead of Williams's Felipe Massa.
Rosberg and Hamilton traded fastest times throughout the session as they began preparations for the penultimate race in their titanic, season-long championship battle.
Hamilton heads into the weekend 24 points clear of Rosberg but the spectre of double points at the final race of the season in Abu Dhabi in two weeks' time means the championship is still wide open.
Hamilton, who has won 10 races this season to Rosberg's four, could win in Brazil and still lose the championship to his team-mate if he hits reliability problems in Abu Dhabi.
Already they seem poised for another private battle for the lead, although predicted wet weather for the weekend adds an element of uncertainty.s
Kvyat was 0.959secs slower than Rosberg and just 0.019secs clear of Alonso.
The Spaniard was on a faster lap, which looked set to move up to within half a second of the Mercedes, right at the end of the session but pulled into the pits before completing it.
Behind Verstappen, Lotus's mini-revival appeared to continue.
Pastor Maldonado scored his first point of the season for Lotus at the US Grand Prix last weekend after a series of new parts came together to provide a boost in performance.
A refined front wing and a new, lighter floor meant Maldonado was more competitive in Austin, Texas, than he had been all season.
He has carried that into Brazil and was seventh fastest in the first session, just ahead of Kimi Raikkonen, who was struggling in the second Ferrari.
The Finn, who has complained all year of struggling with a weak front end, was this time struggling to control the rear, having three spins on the way to being 0.372secs behind Alonso in eighth place.
The McLaren of Kevin Magnussen was ninth and Daniel Ricciardo's Red Bull 10th.
Magnussen's team-mate Jenson Button completed only an installation lap before his car ground to a halt in the entry to the pit lane with a failure of its energy recovery system. He did not get out again.
A number of cars spun on the newly resurfaced track, but there was only one crash.
Force India reserve driver Daniel Juncadella put Sergio Perez's car into the barriers at Turn Six, damaging the nose and front suspension.