In-form Nico Rosberg followed up his Shanghai victory with another commanding performance in the second free practice session for Sunday's Bahrain Grand Prix.
As off-track controversy escalated amid news that Force India would miss the session because of concerns about its personnel travelling back from the circuit after dark, Rosberg emphasised Mercedes' Sakhir speed with a pacesetting one minute 32.816 seconds.
Mark Webber ended up second for Red Bull, 0.446 seconds down on Rosberg, and 0.263 seconds ahead of his team-mate Vettel, who had a near-miss with compatriot Michael Schumacher near the end of the session.
Neither car was damaged, and Schumacher completed the day in fifth, a second off his pacesetting Mercedes team-mate.
The seven-time champion was sandwiched between the two McLarens, with Lewis Hamilton fourth and Jenson Button sixth - 0.9 seconds and 1.4 seconds off Rosberg respectively.
Sauber had an encouraging session, as Kamui Kobayashi and Sergio Perez took seventh and 10th, split by Fernando Alonso's Ferrari and Romain Grosjean's Lotus.
Force India's decision not to take part meant only 22 cars ran, with the Silverstone squad's crew instead getting an early start on preparing the cars for Saturday and qualifying before leaving the circuit.
There were myriad minor excursions over kerbs and run-off areas on the still-dusty track, but no major dramas, incidents or problems, with all the cars that ran completing between 25 and 35 laps.
Pos Driver Team Time
1. Nico Rosberg Mercedes-Mercedes 1m 32.816s
2. Mark Webber Red Bull-Renault 1m 33.262s
3. Sebastian Vettel Red Bull-Renault 1m 33.525s
4. Lewis Hamilton McLaren-Mercedes 1m 33.747s
5. Michael Schumacher Mercedes-Mercedes 1m 33.862s
6. Jenson Button McLaren-Mercedes 1m 34.246s
7. Kamui Kobayashi Sauber-Ferrari 1m 34.411s
8. Fernando Alonso Ferrari-Ferrari 1m 34.449s
9. Romain Grosjean Lotus-Renault 1m 34.615s
10. Sergio Perez Sauber-Ferrari 1m 34.893s
11. Daniel Ricciardo Toro Rosso-Ferrari 1m 34.895s
12. Felipe Massa Ferrari-Ferrari 1m 34.941s
13. Kimi Raikkonen Lotus-Renault 1m 35.183s
14. Jean-Eric Vergne Toro Rosso-Ferrari 1m 35.229s
15. Pastor Maldonado Williams-Renault 1m 35.459s
16. Vitaly Petrov Caterham-Renault 1m 35.913s
17. Heikki Kovalainen Caterham-Renault 1m 35.968s
18. Bruno Senna Williams-Renault 1m 36.169s
19. Timo Glock Marussia-Cosworth 1m 36.587s
20. Charles Pic Marussia-Cosworth 1m 37.803s
21. Pedro de la Rosa HRT-Cosworth 1m 37.812s
22. Narain Karthikeyan HRT-Cosworth 1m 39.649s