McLaren's Lewis Hamilton beat Red Bull's Sebastian Vettel to set the pace in Friday practice for the season-ending Brazilian Grand Prix.
Hamilton beat Vettel by 0.167 seconds. Red Bull's Mark Webber was third from Ferrari's Fernando Alonso.
The top four were covered by 0.206secs as Mercedes driver Michael Schumacher was fifth ahead of Ferrari's Felipe Massa and McLaren's Jenson Button.
The stage is set for a tight battle for victory between McLaren and Red Bull.
As is often the case on this atmospheric, undulating, sweeping track in the middle of the huge Sao Paulo metropolis, the margins between the cars were small.
Just 0.48secs separated Hamilton from Mercedes driver Nico Rosberg in eighth place.
Hamilton said: "The car has been pretty good. It's close, very tight.
"My second lap on the softer tyres seemed very good and the long runs also seem to be quite competitive.
"I think the Red Bulls will still be quicker on race pace. The car feels really good on low fuel, so I might be pleasantly surprised."
Hamilton was further encouraged when he heard that the Red Bulls' rear tyres had suffered some 'blistering' - when the rubber gets too hot and bubbles. But he pointed out that the forecasts suggest the race will be run in wet conditions.
An analysis of lap times suggests Vettel is favourite to take a 15th pole position, which would break the record set by Williams driver Nigel Mansell in 1992.
But their pace on race-simulation runs late in the session suggests Vettel and Hamilton are very closely matched on race pace - although it is always unwise to read too much into Friday practice times.
The Red Bull and McLaren drivers were closely matched in the morning session, with Webber ahead of Button, Hamilton and Vettel and just 0.214secs separating the top four as they ran mainly on the harder 'prime' tyre.
But in the afternoon Button could manage only seventh fastest, struggling to get his car to work on the faster, softer 'option' tyre.
"The car was working pretty well on the 'prime' (tyre)," Button said. "(On) the option tyre I struggled massively. I couldn't get a lap at all on low fuel and on the long run I didn't have the pace either.
"We know some of the reasons, or we know what we can do to help some of the issues, but we just didn't have time to do it.
"The car feels good and I'm sure we can make it (the tyre) work. It's going to be a competitive Saturday. I'm looking forward to it."
Vettel said: "This morning I wasn't too happy. This afternoon I was happier - we were able to improve the cars but we need to make another step."
Ferrari appeared to be struggling on a day when Webber said high track temperatures, humidity and a strong breeze meant setting up the car was a challenge.
Fernando Alonso and Felipe Massa were more than half a second adrift of the top four in the morning session and although Alonso was closer to the pace in the afternoon he was visibly fighting the car.
"In a dry race we are maybe not competitive enough to fight with McLaren and Red Bull," Alonso said.
"Even the Mercedes are quite challenging for us as well coming from behind. So a normal race may be not easy, P5 in qualifying and maybe dreaming of the podium in the race.
"In the rain it is much more open. But after today's practice the rain will be welcome for us."
To add to his woes, Alonso was forced to park his car with five minutes to go in the first session with a failure of an engine that was coming to the end of its scheduled life - the second time in three races that has happened to the Spaniard in practice.
Both Friday practice sessions took place under brilliant blue skies with temperatures of 25C, but the forecast is for thunder storms on Sunday.
Alonso was the second driver to abandon his car - Renault reserve driver Romain Grosjean had earlier pulled off with a clutch problem.
A lot of the teams spent the day dove-tailing preparation for this weekend's race with trying out new parts on their cars, still looking for extra performance even at the end of the season.
BBC F1 pit-lane reporter Ted Kravitz said: "The Ferrari drivers are running development front wings in first practice. Alonso has a brand new one and Massa has the old one that he ended up running in Abu Dhabi but with some little extra cascades.
"McLaren have a new rear wing end-plate and Renault are also playing around with a new suspension in preparation for 2012."
Red Bull also had some new parts, including revised barge boards and a modification to the floor at the rear of the car, a critical part for producing downforce.
This was our last test day and we had some items for next year, too," Webber said. "(It was) a good day for us."