Sebastian Vettel feels he is still "vulnerable" to losing this year's Formula One world title despite currently dominating the sport.

Four successive victories have propelled Vettel into a 13-point lead over Ferrari's Fernando Alonso going into Sunday's Abu Dhabi Grand Prix, with his Red Bull appearing unbeatable.

But Vettel knows one failure is all it would take for the picture to change, and the 24-year-old German has suffered three terminal issues in the last 19 races.

Last year at the Yas Marina circuit, after winning the opening two races at the track in 2009 and 2010 - the latter sealing his first title - Vettel suffered a lap-one puncture after starting from pole.

This season Vettel has suffered two alternator failures, initially at the European Grand Prix in Valencia in June when leading, and again in Italy when running sixth.

The incidents are proof Vettel is far from home and dry yet as he said: "If you look back to the last race in India, which was a great one for us, a couple of laps from the end there were some sparks (from underneath the car).

"Okay, it was not a problem in the end, but it doesn't take much of an imagination to know it could have been.

"If something like this comes up it shows you how vulnerable you are, no matter what position you are in, whether you're in the lead by a big gap or somewhere in the midfield fighting for position."

"Mechanical failures are always in the air, not just for them, but for all of us" - Fernando Alonso

He added: "It doesn't take much and you might end the race not scoring the points you were hoping for, then the whole picture looks different again.

"In 2010, in particular, various people were written off and then written back in again depending on results. That's something we shouldn't forget."

With Ferrari readily conceding they are not the quickest, Alonso can be forgiven for hoping something does fail on Vettel's car.

"Mechanical failures are always in the air, not just for them, but for all of us," said Alonso.

"We know we need to concentrate on our car, our driveability and make sure we have a very strong car that finishes all three races with no mechanical problems.

"If we do have a problem then it will be very difficult to fight for the championship.

"But we know that Red Bull can sometimes be a little more fragile, as we saw in the last race when (Mark) Webber lost KERS.

"So we need to push them. We need to be at the limit throughout the whole race because they have had easy races recently.

"If the KERS fails in Vettel's car nobody notices because he is 10 seconds in front.

"So we cannot have another race with them 10 seconds in front. We need to be right there."

Red Bull go into the race knowing they can clinch a third successive constructors' title as they lead Ferrari by 91 points and McLaren by 101.

Vettel, however, was unaware of the situation until informed by Webber on the flight across from India to Abu Dhabi.

"We were on the same plane and Mark said it would be quite bad for the constructors' if the plane went down," joked Vettel.

"Obviously it would be very special for us to win the championship here, but in order to do so we have to have a strong weekend and score more points than the others."