Michael Schumacher topped the timesheets on the fourth and penultimate day of testing at Barcelona, just two weeks before the first round of the 2011 Formula One season.

Although sunny for most of the day, there were a few times when the sky clouded over and rain threatened, indeed, the general consensus is that there will be rain tomorrow.

Schumacher completed the majority of Mercedes programme with Nico Rosberg taking over for the final hour of the day. The team added a number of new aerodynamic parts to its upgrade package today as Schumacher focused on aerodynamic evaluations and qualifying exercises. Rosberg took over the car at 16:00s to experience the new developments on a dry track ahead of tomorrow's expected rain.

"We have been developing the car step-by-step this week with new parts arriving each day," said Schumacher. "So our focus today has been on understanding how to get the best from the car now that it is pretty much in its final configuration for the first time. The car has behaved as we expected and it's been a very productive day. We completed our programme and I should also be able to get some experience of the expected wet conditions tomorrow."

"First of all, it's super that I was able to do some laps today," added Rosberg, "given the forecast for tomorrow. It was a good few laps, and obviously now that we have most of the developments for the car, it was handling much better and I had a good feeling. So I'm pretty pleased with the situation and would like to thank the whole team for getting everything onto the car that we wanted. We've made good progress over the winter."

Ferrari continues to impress in terms of pace and reliability, Fernando Alonso completing a massive 140 laps and posting a best time just 0.346s shy of Schumacher's.

The Spaniard ran an identical programme to the one brought to a close yesterday by Felipe Massa, centring mainly on a comparison of various aerodynamic elements and then a race weekend simulation.

"Once again, the car has proved to be very reliable, which is always good news," said the two-time champion. "The updates that the team prepared for this last test have improved the handling of the car and today we managed to do a good simulation of a Grand Prix weekend, with reasonable lap times.

"Where are we compared to the others?" he continued. "Today, we are all together here in Barcelona... but joking apart, we will only discover the truth in Melbourne. Tyres used, fuel loads, test programmes: there are too many parameters in play and they can make a big difference in terms of outright performance. Right from the start of these tests, we have always concentrated on our own work, trying to improve the car and be reliable: how clever we have been, we will see in two weeks time."

Nick Heidfeld concluded Lotus Renault GP's pre-season preparations, the German completing 67 laps on his way to posting the fourth best time of the day. High fuel running allowed Heidfeld to improve his understanding of the Pirelli tyres, maximising lap time while looking after the tyres.

According to the team the data confirms the R31 is nicely balanced in terms of tyre wear, with both the front and rears wearing at a similar rate, however, a gearbox problem in the afternoon compromised track time.

"For our final day in Barcelona we started by working on car balance to be ready for Melbourne," said the German. "The set-up work was useful and taught us quite a few things. We would have liked to do more laps and I was hoping to do a race distance later in the day, but the problems with the gearbox after lunch meant we spent a bit too much time in the garage. However, we managed to get out for the final hour and did some running on heavy fuel."

"We had a good morning," said Alan Permane. "The car was working well and showed good pace. The programme involved the continuation of our set-up work from earlier in the week. For the afternoon we had planned a race distance, but unfortunately we had to change the gearbox at lunchtime. In the end we opted to do a very long run on high fuel."

It was a day of mixed fortunes for Williams. Running in the morning, Rubens Barrichello had a fairly trouble free race simulation however, problems in the afternoon meant that Pastor Maldonado only completed 11 laps.

"We lost some time while we changed the engine and then during the installation lap we had another minor engine problem," said the Venezuelan. "In the end I only did one long run but the most important thing was that I got to drive the car with the new aero package which does feel better. Hopefully we will get a full day of running in tomorrow."

"I did a race simulation this morning on some new tyres," added Barrichello. "The car felt OK but we are still not quite where we want to be just yet."