Grosjean, Kobayashi on level in F1 testing

Even split seconds could not separate Romain Grosjean and Kamui Kobayashi at the top of the Formula One test timesheets at Italy's Mugello circuit on Wednesday.

After a day of rain and thunder on Tuesday, the sun shone over the track north of Florence and allowed the 11 teams present to put down some serious mileage.

Lotus's Grosjean and Sauber's Japanese driver both posted a best time of one minute 21.603 seconds.

"It's always good to end the day on top but we have to remember that, in testing, lap times mean very little," said the Frenchman, who took his first podium finish for Lotus at the last race in Bahrain when he was third.

"Having said that, the car felt great and I was very comfortable from the start.

"This test gives us an opportunity to try things that we wouldn't have time to do during a race weekend so hopefully it'll help us to keep pushing forward."

Mercedes's Michael Schumacher, a regular at the Ferrari-owned circuit in his glory years with the Italian team, did the greatest distance with 144 laps or 755km and was eighth quickest.

"We were able to gather really a lot of data and like this we are learning more and more about our car which is absolutely positive," said the 43-year-old seven times champion.

"I am really happy with how things are proceeding with our car and our team," added the German, whose teammate Nico Rosberg handed Mercedes their first win as a works team since 1955 at last month's Chinese Grand Prix.

Red Bull's double world champion Sebastian Vettel was third fastest with Australian team mate Mark Webber fourth and Ferrari's Felipe Massa fifth.

Force India had a frustrating day, with Britain's Paul Di Resta getting out for just 14 laps in the final half hour due to what the team said was an hydraulic problem that kept the car in the garage while mechanics worked on it.