Timo Glock had the best and worst of times in final practice ahead of Sunday's Bahrain Grand Prix.

Glock set the fastest time of the session, and overall over the two days at the Sakhir circuit as he laid down a marker with qualifying looming later on Saturday.

But in sweltering temperatures nudging 40 degrees celsius, and moments after setting a pace equally as scorching with a lap of one minute 32.605 seconds, the German's Toyota ground to a halt.

That came five minutes before the end of the hour-long session, and despite the customary fast-lap frenzy in the closing stages, no-one was able to knock Glock off the top of the timesheets.

Felipe Massa came the closest, suggesting Ferrari's performance may not be as bad as initially feared as last season's title runner-up finished 0.123secs behind Glock.

Nico Rosberg, previously out in front in seven of the 11 practice runs, also gave it his best shot, but was three tenths down in his Williams.

Lewis Hamilton, who on Friday vowed to stand up and be counted as world champion, led the way for a lengthy period until Glock's hot charge. The McLaren driver eventually wound up fourth, 0.370secs adrift, closely followed by Kimi Raikkonen in his Ferrari in fifth.

The top 10 was completed by Renault's Nelson Piquet, Robert Kubica for BMW Sauber, Kazuki Nakajima in his Williams, Jarno Trulli for Toyota and BMW Sauber's Nick Heidfeld. Last week's Chinese Grand Prix winner Sebastian Vettel was 11th in his Red Bull, with Heikki Kovalainen 12th for McLaren and Fernando Alonso 13th with Renault.

Remarkably, the Brawn GP duo of Jenson Button and Rubens Barrichello were down in 15th and 16th, despite both posting their best times in practice, yet they were a second down.

Underlining the competitive nature of F1 these days, the top 18 were covered by a mere 1.1 seconds, with only Giancarlo Fisichella in his Force India and Toro Rosso's Sebastien Bourdais considerably lagging.