Two-time race winner Will Power was fastest in the first practice session for Sunday's Sao Paulo 300, edging Chip Ganassi teammates Dario Franchitti and Scott Dixon.
Power had a lap of 1 minute, 22.3875 seconds in his Penske at the 2.5-mile, 11-turn Anhembi circuit on the streets of South America's biggest city. He was just .0078 in front of three-time defending IndyCar series champion Franchitti.
Dixon finished .3987 behind Power, who is trying to win his third straight race in Sao Paulo. Power also won the last two races heading into Brazil and is the series points leader.
Simon Pagenaud was fourth and Josef Newgarden fifth in a session held in overcast skies but dry conditions.
Rain affected the first two races won by Power in Brazil. The inaugural event was postponed for a day and last year the race was cut short.
Some of the main changes to the track this year aimed to improve the drainage system at the street circuit. Officials also reduced a strong bump near the breaking point for the first chicane, which drivers had complained about last year.
It was the first race in which Honda was allowed to make changes to the turbochargers on its engines, giving the six teams using them an extra boost of power. Honda was permitted to make the change after a three-person panel on Thursday upheld an IndyCar decision against an appeal by Chevrolet.
Five of the top 10 drivers in the first session had Honda engines, including Franchitti and Dixon. The other five were Chevrolet. Lotus also is supplying engines to teams this season. IndyCar has multiple engine manufacturers for the first time in seven years.
The best Brazilian was Power teammate Helio Castroneves, who finished sixth. Rubens Barrichello, in his first race at home since joining IndyCar this season after a 19-year career in Formula One, was 12th fastest, ahead of teammate and fellow Brazilian Tony Kanaan.
''I think I adapted well to the track, it's not too hard,'' the 39-year-old Barrichello said. ''The fans can expect me giving everything I have, their cheers are my fuel.''
Graham Rahal struck a tire barrier exiting a turn and had his session cut short. Oriol Servia also prompted a red flag when his car stopped on the track with a mechanical problem shortly after leaving the pits.
Penske is trying to win its fourth straight race to start the season for the first time in team history in IndyCar.
