Webber was just over a tenth of a second adrift, and whilst Alonso was third quickest, the Spaniard in his Ferrari was 0.599secs down on Vettel, and clearly faces an uphill battle to mount any kind of challenge this weekend.
Just four other drivers finished within a second of Vettel, who is on course to win his third successive title, a feat only achieved previously by Juan Manuel Fangio and Michael Schumacher.
Nico Rosberg in his Mercedes was 0.801secs down, followed by Lotus's Kimi Raikkonen, the Finn a further eight-thousandths of a second behind.
As for McLaren, who have only managed to get both cars home in two of the last seven races to wreck their drivers' title bid and undermine their hopes of a long-overdue constructors' crown, Lewis Hamilton and Jenson Button were left trailing.
Hamilton finished 0.910secs down and Button 0.961secs adrift, with their form of just a few races ago when they had the advantage in Belgium, Italy and Singapore having disappeared.