Lewis Hamilton believes he and McLaren may have a decisive edge over their rivals after he dominated the opening free practice ahead of this weekend's Brazilian Grand Prix.
The 27-year-old Briton, who topped the times in both the morning and afternoon sessions, ended up more than two-tenths of a second faster than defending champion Sebastian Vettel of Red Bull.
"The single-lap pace was really good. I struggled a little bit on the prime tyres, but on the options I was able to get a very good lap out and at the time it was eight-tenths faster than anyone else," said Hamilton.
"Obviously everyone closed the gap towards the end. Sebastian had several tenths and I think he would have got close, but it didn't look like he could match the times, so that's a positive for us.
"But again, we'll see what happens with the fuel loads on Saturday. Qualifying is a different case, but I think we are definitely there or thereabouts this weekend.
"The long runs are the hardest part on the tyres which Red Bull has generally been good at, but we seem quicker than them on the long runs, at least quicker than Mark Webber."
Hamilton will start his 110th and final race for McLaren on Sunday before he leaves to join Mercedes next season.
Team-mate and fellow-Briton Jenson Button was only eighth quickest in the second McLaren as he experimented with a lower-downforce wing.
"It's less downforce but it works in a different way. It's the worst conditions to run a low-downforce car, because in such high temperatures you overheat and slide the tyres," said Button.
"Surprisingly on the long run it's not that bad. It's just on the short runs where you can't use DRS (Drag Reduction System) where you'd like, because you haven't got enough grip."
Meanwhile, the in-form McLaren team believe they have no reason to fear the forecast wet conditions for Sunday's race and can dominate if it rains or remains dry.
Sporting director Sam Michael said he was confident McLaren were able to deal with all conditions.
Michael said: "Last time in the wet we were quite fast, so that is our last data point.
"So, we changed two or three things after that and hopefully those changes means we can be quicker in those conditions. But until you run in the wet you don't know.
"You can always come away thinking you are really good in the wet, and you have a bad race again and it changes."
But Michael said it would be a very difficult challenge to defeat both Red Bull and Ferrari in wet conditions.
"I don't mind what we get, to be honest, I am pretty neutral on it. Coming first and second against Red Bull and Ferrari would be pretty tough, and the weather can go either way on you. We don't mind.
"Our target this weekend is to finish first and second, because if we finish first and second we will finish second in the constructors' championship no matter what happens to anyone else.
"Whether we can achieve that or not remains to be seen. Both drivers were very competitive this morning, but we will try and win it and come second."