Red Bull, Ferrari, Sauber, Lotus Renault and Mercedes all ran their new cars today, while Team Lotus will debut their latest contender tomorrow.
Vettel completed an impressive 93 laps in the Red Bull, with a best of 1m13.769s putting the German almost 0.2s ahead of his countryman Nico Hulkenberg in the updated 2010 Force India.
McLaren test driver Gary Paffet took the team's interim car to third fastest, ahead of Paul di Resta, who replaced his team-mate Hulkenberg in the afternoon.
Speaking to reporters at the end of the day, Vettel played down the importance of topping the time sheets on Day 1.
“It was the first day and it was most important to do laps, which we did – we did around 93 laps and that is quite an achievement and looking back it is something that we never got quite as good on the first day over the last two or three years, so that is a very good sign,” he said.
“On top of it I feel quite comfortable in the car, I enjoyed myself today and I think it was a good start.”
Fernando Alonso put his Ferrari second of the 2011 cars with fifth fastest – some 0.8s behind Vettel.
The Ferrari driver's day ended early when his car stopped on the circuit with a mechanical problem.
The Mercedes and Williams cars also had minor faults on their first day of running, while the new Lotus Renault completed just 28 laps – ending the day 2.6s off the pace.
Two more days of testing in Valencia remain.
See below for the full times from Day 1
|Paul di Resta