Sebastian Vettel has failed to complete three of the nine races and is without a victory so far this season

Red Bull's Sebastian Vettel says Formula 1 can be a "very cruel" sport as he attempts to salvage his season.

The 27-year-old German, champion for the last four years, heads into his home race this weekend sixth in the championship and without a win.

"It's been a tough start, a rough season so far," Vettel said.

"F1 can be fantastic, as I have experience of, but it can be very cruel in retiring from problems. You rely on your car. It is part of the game."

quote Mercedes are in a position to win every race if they want to, so it will be difficult to beat them

Vettel, who was speaking in an interview to be broadcast on BBC One during the highlights of the German Grand Prix on Sunday, has failed to finish three of the nine races so far this season as Red Bull have struggled for pace compared to the dominant Mercedes team.

He is 95 points - nearly four clear victories - behind championship leader Nico Rosberg of Mercedes and 28 points adrift of new team-mate Daniel Ricciardo, who has out-qualified Vettel five times since replacing fellow Australian Mark Webber.

Ricciardo also won the Canadian Grand Prix, where Vettel was third.

Vettel has struggled to come to terms with the new F1 cars following rule changes this season but hopes things will turn around.

"I'm confident it will," he said. "I'm struggling to understand the car so we are testing a lot of things. Some work, some don't."

World Championship standings Nico Rosberg Mercedes 165 Lewis Hamilton Mercedes 161 Daniel Ricciardo Red Bull 98 Fernando Alonso Ferrari 87 Valtteri Bottas Williams 73 Sebastian Vettel Red Bull 70 After 2014 British Grand Prix (13 July)

Vettel added that he was still enjoying F1, despite his problems.

He said: "I have one quote I very often read to myself, from a very good friend: 'Forget the people around you now; remember the little boy who was racing in go-karts, what you were dreaming of and what he wanted to achieve one day and what was his goal. Race for him.'

"I fell in love with the sport, I love racing. The amount of satisfaction I get just going around in a Formula 1 car makes me smile.

"If it is a bad day, then you tend to come out and say it's horrible and you don't enjoy it. But if you had to pick between that and doing nothing, you would always pick that."

Vettel says it would be premature to rule himself out of this year's title race

He insisted he has not given up hope of making up enough ground to win the championship over the remaining 10 races.

"If there is mathematically a chance, there is still a chance," he said.

"If things turn around from this weekend onwards, you'd be stupid not to take the opportunity. So you have to be optimistic.

"Being realistic, though, the gap is very big. Mercedes are in a position to win every race if they want to, so it will be difficult to beat them.

"We are not here to finish third or fifth. If that is the best you can do, you have to be happy with that and respect what other people are doing, but the goal is to win races and fight for the championship."

Watch Sebastian Vettel's interview during BBC Two's highlights of the German Grand Prix from 19:00 BST on Sunday.

German Grand Prix coverage details