McLaren's Lewis Hamilton beat Red Bull's Sebastian Vettel to fastest time in first practice at the season-ending Brazilian Grand Prix.
Red Bull's Mark Webber was third from McLaren's Jenson Button, with Vettel's title rival Fernando Alonso of Ferrari fifth from team-mate Felipe Massa.
Alonso is 13 points behind Vettel and must finish on the podium to have any chance of overhauling the German.
The gap between Red Bull and Ferrari appeared smaller than in recent races.
Lotus's Romain Grosjean was seventh ahead of Force India's Paul di Resta.
On the same tyre, Alonso was 0.465 seconds slower than Vettel's fastest time, a margin that has been almost double that in recent races.
The Spaniard reduced that margin to 0.252secs on a 2013 development tyre that was available to all the teams.
Some of the reduced difference in lap times between Vettel and Alonso will be explained by the relatively short Interlagos lap - times are in the one minute 14 seconds bracket, about 30 seconds slower than at the last few grands prix.
Ferrari were trying out a new front wing in an attempt to do everything they can to give Alonso a chance of winning the title.
While Hamilton was fastest overall, by just 0.009 seconds from Vettel, his best time was also set on a 2013 development tyre.
Vettel's fastest time was set on the standard 2012 'hard' tyre, one of two types available for this weekend's race.
On that, Hamilton was 0.168secs slower than Vettel.
The fastest times were very close between the Red Bull and McLaren drivers - Webber was just 0.058secs slower than Vettel, and Button only 0.019secs behind the Australian.
Williams's Pastor Maldonado was ninth fastest ahead of Force India's Nico Hulkenberg and Mercedes driver Michael Schumacher, who is driving the final race of his career.
Sauber driver Kamui Kobayashi, who the team announced on Friday morning would be replaced by Mexican Esteban Gutierrez next season, was 12th ahead of team-mate Sergio Perez, who is moving to McLaren in 2013.
The second 90-minute session starts at 1600 GMT.
First Practice top 10
1. Lewis Hamilton - McLaren 1:14.131
2. Sebastian Vettel - Red Bull +0.009
3. Mark Webber - Red Bull +0.067
4. Jenson Button - McLaren +0.086
5. Fernando Alonso - Ferrari +0.261
6. Felipe Massa - Ferrari +0.585
7. Romain Grosjean - Lotus +0.588
8. Paul di Resta - Force India +0.607
9. Pastor Maldonado - Williams +0.884
10. Nico Hulkenberg - Force India +0.919