Sepang, Malaysia - BMW-Sauber on Saturday joined three other Formula One teams in an official protest against the diffusers used by Brawn GP, Toyota and Williams.

BMW handed over the relevant documents to officials from the ruling body FIA after the day's qualifying session for the Malaysian Grand Prix.

"This is merely a formal act," said BMW motorsport chief Mario Theissen as BMW joined the appeals of Ferrari, Red Bull and Renault.

The teams are appealing against a decision by Australian GP race stewards that the diffuser designs of the Brawn GP, Williams and Toyota cars are legal.

A hearing is set for April 14 at the FIA headquarters in Paris.

BMW's joining of the appeal in Malaysia means that Brawn, Toyota and Williams could lose points from the Australian and Malaysia races if the FIA deems the aerodynamic devices illegal after all. The Malaysia race is on Sunday.

Brawn drivers Jenson Button and Rubens Barrichello claimed a stunning one-two finish in Australia. Button led the way again as five of the six fastest racers in Saturday's Sepang qualifying used the controversial devices. (dpa)