McLaren's world champion Lewis Hamilton was quickest today on his return to the Belgian Grand Prix circuit where he was stripped of victory last year.
The 24-year-old Briton, Formula One's youngest champion, lapped the fast and sweeping Spa layout in one minute 47.201 seconds after failing to set a time in the day's opening session.
Toyota's Timo Glock was second, 0.016 slower, after Italian team mate Jarno Trulli topped the timesheets in a rainswept morning session.
The sun came out after lunch and Hamilton, who was demoted to third last year for cutting a chicane during a thrilling race, showed that McLaren's recent revival was not confined to tight and twisty tracks.
Toyota, still chasing their first win, also looked surprisingly quick while favourites Red Bull had Australian Mark Webber fourth fastest behind Ferrari's Kimi Raikkonen, who pulled over in the closing seconds.
French rookie Romain Grosjean was an impressive fifth for Renault.
Championship leader Jenson Button, who leads team mate Rubens Barrichello by 18 points, was a distant 17th with the Brazilian 18th. Button had been second in the morning before the rain fell.
Red Bull's Sebastian Vettel, fourth in the championship but 25 points adrift of Button, sat out the first session to save his engines after blowing two in Valencia last weekend but was 10th in the afternoon.
The 22-year-old has only two fresh engines remaining and will collect a 10-place penalty on the starting grid at any race where he has to go over his official allocation of eight engines for the season.
"Having two failures within two days was not a good thing...it affects the programme for the rest of the season," he had said after arriving at the circuit.
"The last thing we want is to take a penalty, so the question now is what can we do.
"We are considering now all our options and possibly this means less running for myself on a Friday, so less practice which for sure is not an advantage."
Ferrari stand-in Luca Badoer, who made his race comeback in Spain last Sunday after nearly a decade's absence, looked ragged on a track that he at least has previous experience of.
The 38-year-old Italian was 10th in the morning, his time flattered by the capricious weather conditions, and then slowest in the afternoon with a time more than two seconds off Hamilton's best.
Badoer, replacing injured Brazilian Felipe Massa, needs a far more convincing drive this weekend after struggling in Valencia. Compatriot Giancarlo Fisichella, who would love to replace Badoer, was sixth fastest for Force India.