Fernando Alonso brought the curtain down on his first test in the new Ferrari F138 with the quickest time on the penultimate day of F1 testing at Catalunya.

The Spaniard posted a time of 1min 21.875secs on Thursday morning, which proved to be the fastest time of the week so far, with teams then largely switching focus to longer runs during the afternoon.

Alonso now hands the car over to Felipe Massa to conclude the test on Friday.

"Today we concentrated on a comparison of the compounds, starting with the soft and moving on to the hard in the afternoon," the Spaniard said. "The track was colder than yesterday, especially in the morning, which made it harder to adapt the car and find the right grip level. We tried various aerodynamic configurations and for the first time, we made some set-up changes to get a good understanding of tyre behaviour and degradation.

"With every change we made, the car reacted as I expected and it was useful to try out the different settings, especially to understand which direction we need to go in next week, when there will be a greater emphasis on performance. Once again this year, the tyres will be one of the crucial aspects to manage: they are softer and quicker, but also less consistent and they degrade rapidly with every lap. We will have a lot of work to do to understand how best to balance the car, but that applies to all the teams."

Behind Alonso, it was a good day for Nico Hulkenberg, as a strong lap shortly before lunch - also on the soft Pirelli tyre - proved to be good enough for second place at the wheel of his Sauber. It also saw him edge out the Lotus of Romain Grosjean on the times, as the Frenchman enjoyed a trouble-free day at the wheel of the E21.

That was in stark contrast to the issues faced by Kimi Raikkonen on the first two days, with Grosjean completing a total of 119 laps working through a programme that included the first full race simulation for the new Lotus challenger.

"I think I'm ready for a sleep after so many laps in the car!" he quipped. "It's good to see reliability today to add to the pace we've already seen in the car. We're still at an early stage of development so it's really promising to see where we are. It was difficult out on track as temperatures were so low, but we've gained a lot of useful data. The 2013 tyres certainly feel different from last year's but already we're starting to understand them. I hope it's dry tomorrow so we can get some more laps under our belt."

Nico Rosberg was also busy as he returned to action for Mercedes, completing 107 laps; the best of which came on the medium tyre, unlike the three drivers ahead.

Williams pair Pastor Maldonado and Valtteri Bottas took fifth and sixth on the timesheets as they shared driving duties in the FW35, both working on race simulations in the process, while Jenson Button and the returning Adrian Sutil rounded out the top eight.

Having endured some technical issues on Wednesday, Thursday passed without drama for defending champions Red Bull, with Mark Webber managing to join the 100 lap club on his first appearance of the weekend at the wheel of the RB9.

"We had a pretty good run today, we're learning plenty, so a positive outing for us," he said. "Overall the car ran smoothly and once again we amassed a huge amount of data for the guys back at the factory to go through. We'd like to get a bit more mileage tomorrow in the dry, but that doesn't look like it's going to happen, it looks like it will be wet.

"As usual at tests, the question of the pecking order comes up all the time but, honestly, I have no idea. There are a few quick cars out there, but in winter testing it's so hard to say if anyone's better than anyone else, especially with the tyres going off the way they are - you're losing four or five seconds over the course of a stint, so figuring out who's doing what is pretty difficult. All we can do is keep pushing, keep developing and keep our eyes fixed on the first race."

Jean-Eric Vergne was tenth for Toro Rosso, followed by Max Chilton and Giedo van der Garde - the latter causing the only red flag of the day late on when he stopped on track.

To see times from day three, CLICK HERE.