Mark Webber completed a Friday practice double after narrowly beating Jenson Button to the top of the time-sheets in Malaysia.
Webber, 34, was only five-thousands of a second quicker than the 2009 world champion when the chequered flag dropped.
Lewis Hamilton and Sebastian Vettel ensured a Red Bull-McLaren lockout at the front by winding up third and fourth respectively.
Mercedes’ Michael Schumacher was fifth ahead of Felipe Massa. Fernando Alonso struggled to ninth fastest.
But it was Webber’s day as he set the fastest lap in both morning and afternoon practice sessions although the second practice was much tighter after having obliterated the field earlier in the day.
Webber played down his ominous weekend form and said there was still a long way to go.
But Hamilton was more pessimistic about his chances and said Red Bull still hold a significant advantage over the chasing pack.
“I think Red Bull are always blowing smoke up other people. I’m sure they have got half a second at least to pull out tomorrow.
“Red Bull are using KERS now this weekend, so that cancels the advantage that we may have had,” said Hamilton.
Ferrari endured a frustrating day throughout as Massa and Alonso finished sixth and ninth respectively in both sessions.
“A difficult day in Sepang” and “far away from the leaders” was how the Italian team described their Friday running on Twitter.
Alonso was downbeat about his chances of a good result this weekend but remained optimistic for the rest of the season.
“Obviously we know that we need to keep working tonight, to keep changing what we can improve in the car, and be more competitive tomorrow.
“This is only the start of the season. We are not quick enough to fight for the win and pole position, but that does not mean that we have to throw in the towel,” Alonso said.
Mercedes enjoyed a better day with Schumacher twice in the top-five.
“We definitely made a step in the right direction. We were closer to our level of performance from Barcelona than in Melbourne and I am hopeful there will be more to come,” said the seven-time world champion.
Team Principal Ross Brawn said: “We have had a much better day here than we experienced in Melbourne. There are some issues which we need to look into and resolve but it is, without doubt, a more positive start to the race weekend.”
Hispania endured another difficult day at the other end of the grid. Narain Karthikeyan and Vitantonio Liuzzi both suffered technical failures and ended up bottom of the standings.
But in the second session Karthikeyan did set a time within 107% of Webber’s which would be good enough to allow him to race on Sunday.
“Feels good to get some running. Lot of work to be done, but feel positive for qualifying! Glad to be within the 107%,” he tweeted.