Formula 1 world championship leader Sebastian Vettel believes it is unreasonable for his critics to attribute much of his success to Red Bull's car advantage.

Vettel is on the brink of claiming a third successive title in Brazil this weekend.

He took four wins in a row from the Singapore to Indian Grands Prix as he caught up and overhauled points leader Fernando Alonso, whose Ferrari has been less competitive than the Red Bull for most of the 2012 season.

But asked if he felt his reputation would be higher if he did not have an often-dominant car, Vettel argued that he had done his time in backmarker teams and no champions achieved their results in midfield machinery.

"I think if you look back I don't know how far, as far as I can look back, there were never people really, really successful in a really bad car," he said.

"It is a natural thing to happen: one day you have a strong driver in a strong team so you end up with a strong combination and that is difficult to beat.

"It's natural to be in a weaker car. We have all been in that situation. Michael [Schumacher] started in a Jordan, which was not competitive, but had some highlights, Fernando started in a Minardi and set some highlights.

"I started at BMW replacing Robert [Kubica] for one race, which was a great chance, and then afterwards got the seat in Toro Rosso, which at the time was not a competitive car, but we did a good job and even won a race.

"We had a great season, the step up to Red Bull Racing was great fun and a fantastic season - the first time to be competitive, finish on the podium and win races.

"It was a fairly normal way I went."

Vettel said he was open-minded about what would happen at Interlagos, despite Red Bull having won the last three races at the circuit and his relatively comfortable 13-point cushion.

"It is sport and anything can happen," he said. "We need to look after ourselves.

"The weekend starts tomorrow morning and not on Sunday.

"We have to go step by step, to make sure we get the maximum result.

"Historically we have been very quick here. We know it is a place where lots of things can happen. We need to be sharp in the moment to see what we can get."

CHAMPIONSHIP PERMUTATIONS

VETTEL WINS THE TITLE IF:

- He finishes in the top four 
- He finishes fifth, sixth or seventh and Alonso doesn't win 
- He finishes eighth or ninth and Alonso is third or lower 
- He finishes 10th or worse and Alonso isn't on the podium

ALONSO WINS THE TITLE IF:

- He wins and Vettel is fifth or lower 
- He is second and Vettel eighth or lower 
- He is third and Vettel is 10th or lower