World championship favourites Lewis Hamilton and Kimi Raikkonen set the fastest times in Friday practice ahead of Sunday's Australian Grand Prix.
Hamilton is hopeful of a strong showing at the year's first race
World champion Raikkonen's Ferrari set the fastest time of the day to be 0.487 seconds quicker than Hamilton's McLaren in the first session.
But the Briton was on top in the afternoon, with Raikkonen sixth.
Hamilton, 23, said he felt "very, very optimistic" for Sunday's race. "The pace we and the Ferraris have is good."
Ferrari's Felipe Massa was third in both sessions, with Fernando Alonso sixth and 13th in his Renault.
Ferrari look strong, but it's still too early to tell exactly where we are in comparison
Hamilton's McLaren team-mate Heikki Kovalainen was fourth fastest in both sessions.
The pace of the Red Bull also caught the eye - Australian Mark Webber was second fastest in the afternoon session and fifth fastest in the morning, while team-mate David Coulthard, of Scotland, was fifth fastest in the afternoon.
That seems to back up Webber's claim in his BBC Sport column that Red Bull have been consistently the third or fourth quickest team in pre-season testing.
The practice sessions took place in searing temperatures, with a high of 38C. Coulthard told 5 Live that the cockpit temperature of his car was pushing 60C.
"We're absolutely roasting in the cockpit," Hamilton said. "It's like having four jumpers on and shorts and trousers in the sauna."
Raikkonen's Ferrari looked ominously quick in the first session
Inconclusive though lap times in Friday practice can be, they suggest what many in Formula One suspected - that McLaren and Ferrari have an advantage of almost a second a lap over the rest of the field.
They also suggest that, as predicted, the battle for the lower points positions will be closely fought.
BBC Radio 5 Live commentator David Croft said: "The fight for the championship will be between two teams - Ferrari and McLaren.
"And we'll have two distinct battles - the fight for the title and the midfield battle, which will include Williams and Renault and BMW and maybe even Toyota."
Hamilton said: "It's great to be back racing and being here in Melbourne where I started my Formula 1 career only a year ago.
"It's always a special feeling to go out of the garage for the first time in practice at the start of a new season.
"There was some good progress with the car, and we made the best use of the ever-improving track conditions.
"Ferrari look strong, but it's still too early to tell exactly where we are in comparison. All in all, a good start to the Australian Grand Prix and the season."
Raikkonen, who won in Melbourne last year, was less pleased with his Ferrari.
"I'm not very happy with the way practice went," he said. "This morning we found some good settings for the car but in the afternoon we struggled and our lap times reflect that.
"We must look carefully at the data to work out how to improve the car."
Coulthard was impressively quick despite this off-track moment
And the performance of the Hondas appears not to be as bad as many had predicted, with Englishman Jenson Button 11th in both sessions.
The struggling team said they had continued progress from an encouraging final test of the winter at the Spanish Jerez track two weeks ago, when they introduced new parts to improve the car's aerodynamics.
"It has been a good day for us," Button said. "We focused mainly on tyre work and getting the best out of the car in the very hot conditions. Everything went smoothly and the car feels much as it did at the Jerez test, which is pleasing."
Button's former team Williams, by contrast, had a frustrating day.
They have been battling for the lead of the group behind Ferrari and McLaren in winter testing, but gearbox problems hit both cars on Friday and lead driver Nico Rosberg missed the entire first session.
• McLaren test driver Pedro de la Rosa has been elected chairman of the Grand Prix Drivers' Association - and said one of his first aims was to persuade stars who are not yet members, including Hamilton and Raikkonen, to join.
De la Rosa said: "One of the big aims is to recruit all of the drivers, not only the new youngsters but everyone. We all have to be part of it because we are working on safety and safety is for everyone. That's the whole point of the GPDA."
Double world champion Alonso and Webber are the other two directors of the GPDA.
First practice times from Australian Grand Prix at Albert Park, Melbourne:
1. Kimi Raikkonen (Fin) Ferrari one minute 26.461 seconds
2. Lewis Hamilton (GB) McLaren-Mercedes 1:26.948
3. Felipe Massa (Brz) Ferrari 1:26.958
4. Heikki Kovalainen (Fin) McLaren-Mercedes 1:27.114
5. Mark Webber (Aus) Red Bull-Renault 1:28.263
6. Fernando Alonso (Spa) Renault 1:28.360
7. Robert Kubica (Pol) BMW Sauber 1:28.579
8. Timo Glock (Ger) Toyota 1:28.913
9. Sebastian Vettel (Ger) Toro Rosso-Ferrari 1:28.957
10. Jarno Trulli (Ita) Toyota 1:29.014
11. Jenson Button (GB) Honda 1:29.124
12. Giancarlo Fisichella (Ita) Force India-Ferrari 1:29.230
13. David Coulthard (GB) Red Bull-Renault 1:29.301
14. Sebastien Bourdais (Fra) Toro Rosso-Ferrari 1:29.363
15. Rubens Barrichello (Brz) Honda 1:29.533
16. Nick Heidfeld (Ger) BMW Sauber 1:29.561
17. Adrian Sutil (Ger) Force India-Ferrari 1:30.155
18. Nelson Piquet Jr (Brz) Renault 1:30.357
19. Takuma Sato (Jpn) Super Aguri-Honda 1:31.048
20. Anthony Davidson (GB) Super Aguri-Honda 1:31.771
21. Kazuki Nakajima (Jpn) Williams-Toyota 1:35.053
22. Nico Rosberg (Ger) Williams-Toyota no time
1. Hamilton 1:26.559
2. Webber 1:27.473
3. Massa 1:27.640
4. Kovalainen 1:27.683
5. Coulthard 1:28.037
6. Raikkonen 1:28.208
7. Trulli 1:28.292
8. Rosberg 1:28.352
9. Fisichella 1:28.469
10. Glock 1:28.582
11. Button 1:28.632
12. Heidfeld 1:28.731
13. Alonso 1:28.779
14. Barrichello 1:28.849
15. Kubica 1:28.860
16. Nakajima 1:29.077
17. Sutil 1:29.161
18. Vettel 1:29.193
19. Piquet Jr 1:29.581
20. Bourdais 1:29.605
21. Sato 1:30.663
22. Davidson 1:31.527
Follow live coverage of the Australian Grand Prix on 5 Live and bbc.co.uk/sport. Qualifying starts at 0300 GMT on Saturday with the race at 0430 on Sunday.