World Champion Jenson Button expressed himself satisfied with his first grand prix day as a McLaren driver after setting the fourth-fastest time in the second free practice session for the Bahrain Grand Prix.
The Briton who effectively matched teammate Lewis Hamilton's pace through the two 90-minute sessions said that while his low-fuel runs were affected by traffic, he was encouraged by his MP4-25s performances over the longer stints.
"The long runs seem to be positive," he said. "The car is going toward over steer, but that's the same for everyone and it is about managing that situation.
"I am reasonably happy with the basic car, but there are areas we need to work on with setup, which we would like to have done in the second session. It's so busy and you've got to really do a tire back to back, and run new tires to see where the car is. We know where it is now and where we want the car to be so it's not so bad.
"We will have a long evening and hopefully find some improvements overnight. The shorter runs were frustrating because of the traffic but the long runs seemed reasonably good. I'm quite happy."
Button added that there is a distinct difference in the cars' behavior when running on full tanks and low fuel: "I think everyone likes it with less fuel because you can do a lot more with the car.
"When it is heavy, it is a little bit too lazy," he added. "That sounds crazy, calling an F1 car lazy, but it is. Any bump on the circuit you really feel and it exaggerates any problem that you do have. So low fuel is better, but high fuel; our pace was OK today but we still need to work on it."
Button admitted that he felt more relaxed returning this year as a World Champion, but warned his rivals that he will be no less competitive now that he has achieved his goal of winning the title.
"When you have achieved your goal, you can think 'I have done that, what do I do now?'," he said. "But while I did think that after Brazil, I have chosen my new challenge which is to race here, which is very exciting to me. I think I needed that challenge. I am very relaxed but in a positive way, not a negative way. I am so hungry, you can't believe it. As a driver and as an F1 fan this should be an exceptional season and that obviously gets you excited."
Button dodged questions about McLaren's new controversial F-duct system, which is alleged to stall airflow around the rear wing of the car. The system was given the all-clear and approved by the FIA scruntineer, but has been branded by rival teams as against the spirit of the regulations.
"Our wing is our wing, and that's the way it is," said Button. "There is no problem with it, it has been passed by the authorities a couple of weeks ago. That's it.
"It's an exciting, innovative design and it seems to be working well. I think we would all love more downforce in the cars – we don't have that at the moment – but the straight-line speed is reasonably good."