Sebastian Vettel is switching to a different Red Bull chassis this weekend in a desperate bid to salvage his title defence after being outpaced by rivals Mercedes so far this year.
The four-time world champion said it was a move that was aimed at helping the team to understand why the German driver had languished behind his rivals, including new Red Bull team-mate, Australian Daniel Ricciardo.
"I think we concluded after China, where we were quite a little bit behind, to change the chassis," Vettel said.
"It is not a new chassis, it is an old one we used in testing in the winter and we have some experience with it.
"It is just to try everything we can."
Vettel explained that he was making the move for this weekend's Spanish Grand Prix in case car problems contributed to his recent struggles.
Although he finished on the podium in Malaysia, he was only sixth and fifth in the following races in Bahrain and China -- and had to move aside for team-mate Ricciardo on both occasions.
Notably, when Red Bull confirmed Vettel would use a new chassis in Spain, the team suggested it was a scheduled move.
But Vettel said the decision was made after Shanghai as part of an effort to ensure every possible cause of his troubles was investigated.
He told reporters: "It is not unusual to change chassis generally, we decided to change back to an older chassis just to make sure that nothing is wrong."