But Renault have also introduced bodywork modifications and Button expects their progress to keep Fernando Alonso and Giancarlo Fisichella out of his clutches at Interlagos this weekend.

Button revealed the improved car has delivered better performance but tipped Renault’s gains to exceed BAR’s.

He said: “I think we are going to be competitive against most teams like Ferrari and Toyota but I think Renault have actually also made a good step forward with their car, supposedly that is about half a second, so that is going to be slightly different.

“Our long runs are not too bad and that is what you need here, you need the consistency, so at least we have that.

“It is difficult to say on our new aerodynamic package because we have not had both here, but it has given us more downforce front and rear, so that is good.”

Button and his BAR engineers have work to do this morning to fine-tune the car’s set-up after a difficult start to practice in Sao Paulo.

The 25-year-old was an encouraging fourth in first practice but slumped to 17th in the second session after suffering handling problems, giving him a headache ahead of today’s qualifying session.

“It just felt like we had really low grip,” he added. “We have got some balance issues as well which, realistically, is a good thing because we can look at the car and make improvements, instead of just having low grip like we have had before.

“We can really work with the car now and make the difference. It is not all bad.”

Button’s improved results in the second half of this season have been overshadowed by the battle for world championship honours, and that situation is likely to continue this weekend.

Alonso needs only to finish in the top three to secure his maiden title, ending Kimi Raikkonen’s challenge.

Button hopes his former Renault colleague does not tie up the title just yet though, adding: “I hope the championship is not decided here because we still need the excitement in the final two races. I don’t think it will be decided here.

“I am looking forward to the last two races, it is obviously leaning towards Alonso winning the championship but I still think Kimi has a chance.”

Alex Wurz was the man to beat in practice yesterday, setting the fastest time in both sessions.

The McLaren test driver’s time from the first session, one minute 11.701 seconds, was better than any of his rivals managed through that hour and the afternoon practice, which he again topped.

In the championship chase, honours were even between Alonso and Raikkonen. The Spaniard was third in first practice, beating Raikkonen, before slipping to 11th in the second.