LONDON Daniel Ricciardo tested for Formula One champions Red Bull at Silverstone on Thursday but went quickest in his regular Toro Rosso race car.
The Australian, battling Finland's 2007 world champion Kimi Raikkonen for the Red Bull seat to be vacated by Mark Webber at the end of the season, drove for both Red Bull-owned teams on the second day of a young driver test.
The Toro Rosso race driver set the day's fastest time of one minute 32.972 seconds with his current team before lunch.
The Australian then switched to the Red Bull and set a time of 1:33.187, the third fastest of the day. He was also left red faced when he ran into the gravel after just seven laps and stopped the session.
"Just my mistake. I was probably pushing a bit too hard," he told reporters.
Red Bull team principal Christian Horner had said on Thursday that they were "keen to have a look at Daniel as a prospect for next year."
Spaniard Carlos Sainz junior, 18-year-old son of the retired world rally champion, was an impressive second fastest for Toro Rosso in 1:33.016 on his first F1 outing. He will test the Red Bull on Friday.
Venezuelan Pastor Maldonado, one of four regular race drivers on the track on Thursday, tested the new type of Pirelli tires to be introduced at next week's Hungarian Grand Prix.
"The tires feel quite different but we need to see how we compare against other cars on the track with the same compounds," said the Williams driver.
"We didn't get performance from the car with them so we need more time in Hungary as we couldn't make any set up changes today."
Susie Wolff, the team's female development driver, will be in the car on Friday in her first proper Formula One test.
(Reporting by Alan Baldwin, editing by Ken Ferris)