Kimi Raikkonen returned Lotus to the top of the timesheets on the final day of the opening F1 group test at Jerez, while Lewis Hamilton underlined the inherent reliability of his new Mercedes by posting the greatest number of laps.

While no-one came close to matching the scintillating softer-compound time posted by Ferrari's Felipe Massa on Thursday - Raikkonen's best effort remained three-tenths shy of the Brazilian's 1min 17.879secs mark - the leading group remained close throughout what turned into an eight and a half hour session, following a 50-minute hiatus to repair a small pot-hole that appeared at turn nine around lunch-time.

Raikkonen led the way after a couple of hours and was always there or thereabouts in terms of pace, but appeared in line for another low lap tally until ramping up his work in the final phase of the day, eventually accumulating 82 tours to add to the clutch-afflicted 40 he managed on day three. The Finn ran through a continued programme of aerodynamic assessments and exhaust exit evaluations, but was typically unimpressed with his position at the head of the times.

"We continued our work from yesterday and made some good progress," he reported, "We're at the top of the timing monitors, but that means nothing in testing. Our focus has been testing parts on the car, but I've been able to get the set-up more to my liking.

"For sure, there's more work to be done in this area, but that's what we're here for. The car feels strong and we seem to have a good idea of where we're going with improvements. Let's see what happens in Barcelona."

Raikkonen's closest rival only completed 56 laps in two-thirds of a day before handing back to the man whom he could partner in this year's Force India line-up but, as an audition, it could hardly have gone better for Jules Bianchi.

"My first experience of the new car was very positive and it's clearly an improvement over last year's car," the Frenchman opined, "I spent most of the time on the medium tyres, but I got a chance to run the softs as well and they offered a lot of grip. It was also nice to do some long runs, so I've felt the car on heavy fuel, which is good for my experience. I'm pleased the team asked me to help out this week and I'm happy with how things went today."

World champion Sebastian Vettel again had to settle for third spot, as he had on Thursday, but racked up another 96 laps as the Red Bull RB9 proved reliable once more.

"I think, for the whole team, it's been quite a good test," he said, "No problems in terms of reliability and we did a lot of laps, so I'm quite pleased with the results. I feel a bit better than last year. I think we had some issues with reliability then, so it seems we have done our homework well.

"Looking ahead, I think the Barcelona test will maybe reveal a bit more, but just because people are running more and teams will play around a bit more there. If you keep your eyes open you might spot some stuff, but, as I've said before, we just focus on what we do. In Barcelona, we'll learn more about ourselves and maybe a little bit about our rivals. It should be interesting."

Esteban Gutierrez laid claim to the biggest workload of the day after covering 142 laps in the Sauber, but Jean-Eric Vergne was just a tenth behind the GP2 graduate after another solid day in the Toro Rosso. Having run second to Raikkonen early on, the Frenchman's programme saw him slip back down the order, but he left Jerez happy with the progress that had been made.

"In terms of pure mechanical understanding of the car, we've made a significant step forward compared to last year and, specifically today, we got through all our planned work programme," he claimed, "I am much more confident about the new car than I was before the test and it gives me a good feeling from behind the wheel.

"One of the aims of the design team was to give us drivers a car with a broader operating range in terms of set-up options and I can already say they have succeeded in that point. There is still a lot to do, so I'm looking forward to my next session in Barcelona."

Hamilton's mammoth effort came up just three laps shy of replicating team-mate Nico Rosberg's from day three, despite the Briton doubting that such a total could be achieved with fewer laps than the German on the board at lunch. With none of the niggling reliability woes that afflicted the pair over the opening couple of days, Hamilton concentrated on set-up changes as he continued to familiarise himself with the W04, but completed a race distance after the enforced break to bring the team's total up to 1426km for the four days.

"Today, we managed the kind of mileage that the car is capable of and I think we have a good platform to start working from," the Briton noted, "Now we need to understand the W04 even more. Personally, I am learning something with every lap I do and every change I make to the set-up but, overall, I think we are probably at the level we would have hoped to be."

Once again, Hamilton ended the day ahead of the man who replaces him at McLaren this season, with Sergio Perez one place and four-hundredths shy in seventh overall. Following a similar pattern to the past three days, the Mexican's day began with some aero correlation work, conducted over a number of shorter runs, before the team turned its attention to mechanical set-up work. The afternoon was then spent carrying out a series of longer runs - with live pit-stops - to more fully understand the set-up changes.

Valtteri Bottas got his second day in the cockpit of the 2012-spec Williams, aware that the next time he hits the track it should be in the car that he will campaign for the rest of the year.

"We have gone through a complete programme testing various parts that will be used on the FW35," technical director Mike Coughlan confirmed, "This compliments our current philosophy of using rigs to pass off systems before running them on the car. The drivers have enjoyed themselves running through tyre comparisons and set-up changes that you would be reluctant to do at a race meeting due to time constraints and, although these results have been a little compromised by the very aggressive nature of the track surface here, we have acquired some useful data to carry forward. We now look forward to the next test in Barcelona and the launch of the FW35."

After Massa's heroics on Thursday, Pedro de la Rosa would have expected more from his first run in the F138 but, despite only attempting to gather reference points for his work in the simulator at Maranello, the Spaniard was frustrated to spend all morning on the sidelines after a fire broke out in his car after just two laps.

The team worked for the rest of the morning to put right what turned out to be a gearbox issue and the afternoon proved more productive, especially as the end of testing was put back by half an hour. de le Rosa was thus able to complete his programme, which had been revised as a result of the long stop in the garage and focused mainly on testing various aerodynamic configurations.

"I had a lot of mixed feelings today," the Spaniard admitted, "I was very excited to drive the car but, when I got out after the first two laps, I was not exactly happy. All my life I've been waiting for an opportunity like this and to see it end after just a few corners was definitely not nice, especially because I wasn't sure that we would be able to continue with the programme. It was vital to get back on track given how few days are available to us, and that will be very important when it comes to comparing the data with the simulator as we develop the car."

Charles Pic and Luiz Razia again occupied the bottom couple of spots on the timesheet for much of the day, as they continued to get to grips with the new Caterham and Marussia respectively. Several seconds divided the pair for much of the day, before Razia embarked on some performance tests and quickly closed the gap. Both ended the day some three seconds off Raikkonen's pace, but put in some good mileage, with Pic the third driver on the day to break 100 laps.

"109 laps today is a good way to finish the first test," the Frenchman acknowledged, "The track was colder this morning than the first three days, so it was tricky getting the tyres to work, but we completed all the programmes we'd set for the day and we have some very useful information to work on - and some interesting options to look
at for the next test.

"One key part of this test was to work on getting the most out of KERS and we've definitely made good progress. There's still more to come from that, especially maximising its performance under braking, but I'm really happy with what we've worked through and can't wait to get back in the car in Barcelona."

Further race distance mileage was the order of the day at Marussia, but the programme was not without its frustrations. Although Razia posted improved lap times through both the distance and performance work, his runs were somewhat stilted which prevented him gathering any real momentum.

"It is unfortunate that we didn't get the smooth day of running we hoped for, but we have to be happy to have completed most of our programme with the MR02 this week," the Brazilian conceded, "Testing is the place to work through our problems, so we don't have to find them during the season, and resolving these is in itself good progress.

"I got the chance to do some of the planned performance work later on, but I didn't get a clear shot at it, so I don't feel like I ended the day where I could have been in terms of lap time. What is good is that there is a lot of potential and we can see this very clearly. I'm very excited about the next two tests and I expect to see us making good steps forward."

di Resta again returned to the track for a short cameo appearance in the Force India but, as on Thursday, remained in twelfth spot when the chequered flag fell, despite completing 49 laps after taking over from Bianchi.

Testing resumes in Barcelona on 19 February.