Red Bull's Mark Webber set the quickest time in the first practice session for the 2013 Malaysian GP on Friday (March 22), the Australian edging out Melbourne winner Kimi Raikkonen's Lotus on a hot and steamy morning in Sepang.As was the case in the season-opening race in Australia (March 17), the Red Bulls showed plenty of one-lap pace, Webber's team mate Sebastian Vettel was third fastest, while the Lotus appeared the most adept at managing tyre degradation.TOP FORMWebber topped the timesheets with a lap of 1min36.935, just 0.068 seconds ahead of Raikkonen, who lost 40 minutes of the session as Lotus mechanics changed the car's KERS battery following his installation lap.World champion Vettel clocked 1min37.104 in the second Red Bull, marginally ahead of Fernando Alonso's Ferrari, who won this race in 2012, and Nico Rosberg's Mercedes.Alonso's team mate Felipe Massa was sandwiched between the Force India pair Adrian Sutil (sixth) and Paul di Resta (eighth), who backed up a solid performance in Melbourne with another strong showing around the demanding Sepang Circuit.Lewis Hamilton was ninth fastest in his Mercedes, while Romain Grosjean rounded out the top 10 in the second Lotus as both McLarens again struggled with tyre wear and lapped more than a second behind Webber in the 90-minute session.Mindful of the rapid tyre wear experienced with this year's Pirellis, all 22 drivers opted to complete one or two installation laps at the start of the session before returning to the pits and watching the clock tick down to the final hour.RACE SIMULATIONFans would have been disappointed to have arrived at the track early and not see any action after the early flurry of activity, until the cars returned to the circuit to set timed laps on low fuel loads for the second 30 minutes of the session.Mercedes team principal Ross Brawn said: "We are trying to find the optimum time to run the cars but we appreciate the concerns of the fans, who want to see cars on the track.""It may be a good idea to have a sacrificial set of tyres for us to use in practice."The final 30 minutes of the session was dedicated to race simulation runs on heavier fuel loads as Vettel - who complained of feeling a lot of vibration after completing 16 laps on his worn hard tyres - and Rosberg got through the most work.Earlier, Hamilton explained how he had prepared for the extreme temperatures in Malaysia so quickly after arriving from a relatively chilly Melbourne in March 2013."As soon as I landed, I started sweating. You need to drink around four to five litres of liquid a day," the Briton told the BBC."I was in the sauna last night, sweating it all out and trying to get used to the temperatures. You just need to spend as much time in the heat as you can to get your body to acclimatise."The second free practice session is due to start at 8am SA local.Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.