A late lap from Lewis Hamilton offered a tantilising glimpse of what qualifying for the Australian Grand Prix could look like, with the best times of Ferrari and Mercedes split by a fraction of a second at the end of the final day of preseason testing.
The common consensus which had formed over the previous seven days had been that Ferrari held the advantage, with a perfect start to testing and a series of impressive times throughout the two weeks the teams have been at Barcelona's Circuit de Catalunya. Sebastian Vettel's 1:16.221 was the quickest mark set throughout the entirety of testing, just 0.01s quicker than Ferrari teammate Charles Leclerc had set on Thursday while Mercedes focused on longer runs and a red-flag disrupted race simulation.
Late in the evening, we got our first comparable lap from Mercedes. Just hours after he had predicted Ferrari's advantage was around half a second per lap, Lewis Hamilton ventured out to the circuit on a set of Pirelli's softest and grippiest tyres, the C5s, and crossed just 0.003s shy of Vettel's headline time over the 4.655 km (2.892 mile) circuit.
The lap may well raise suspicions the world champions have been 'sand-bagging' -- the term given to a team masking its true performance -- although there is no perfect way to measure or compare either. However, the 1:16.7 Vettel set on the C3s before lunch and the 1:16.6 set by Hamilton on the C4s in the evening suggests both cars have much more performance left to find.
Fuel loads remain the biggest unknown in testing and a crucial variable -- the heavier the car, the slower it goes, meaning teams can adjust the amount in their tank to either mask or exaggerate raw pace. Time of day is also a factor: Vettel's run of three qualifying simulations took place in the 60 minutes before lunch, when the track was at its hottest, while Hamilton's were set as the temperature cooled in the final hour of the session. The heat of the track will have impacted the performance of the tyres in different ways.
Both teams accumulated healthy mileage in the day, although Ferrari was forced to end its preseason 90 minutes early when Vettel stopped on the exit of Turn 2. The team later confirmed it had been caused by an electrical issue.
Although Ferrari's pace has been impressive this winter, this week has not been without problems. Friday was the third consecutive day the team had encountered a car issue. On Wednesday Vettel crashed heavily at Turn 3 after a wheel rim failure, while Leclerc lost a chunk of track time to a problem with the car exhaust. Testing is the perfect time to iron out reliability gremlins but, on the evidence of testing, Ferrari heads to Melbourne's Albert Park circuit with the more fragile of the two cars expected to fight for the race win.
Mercedes and Ferrari's nearest rivals also had a trying day --Max Verstappen accumulated just 29 laps for Red Bull after missing the entire afternoon session. The former world champions had to rebuild the car after Pierre Gasly's heavy crash on Thursday afternoon. Despite reverting back to old parts so Verstappen could hit the track, a gearbox issue delayed him for most of the day. Red Bull heads to Melbourne having not offered any true glimpse of its outright pace in the same way Mercedes and Ferrari did in week two.
The remaining seven teams all enjoyed productive days. Carlos Sainz led the mileage chart for McLaren with 134 laps. The British team will be very happy with its low-key testing, which included none of the major dramas of previous years, although it is still hard to see the team being at the front end of the midfield at this stage in the year. Kimi Raikkonen managed just two laps fewer in the Alfa Romeo car which many in the paddock believe could be leading that pack in Melbourne, although midfield rivals Renault also split 103 between Nico Hulkenberg and Daniel Ricciardo either side of lunch.
Haas managed to avoid any of major dramas until the final half an hour, when Kevin Magnussen stopped on track during his 94th lap of the circuit. Romain Grosjean had completed 73 laps of his own in the morning -- as last week, Haas completes this test with its strongest haul of laps on the final day. Given the team's loss of tack time earlier in the week, it did not spend too much time focusing on short-run pace -- Magnussen appeared to be nearing the end of a race simulation when he stopped. Magnussen's stoppage prompted one of the day's three red flags, with the others being triggered by Vettel's electrical issue and a mid-morning issue for Raikkonen.
Williams had an encouraging final day, with Robert Kubica's 90 laps his last until he competes in his first grand prix weekend since 2010. However, it still finished below Racing Point, another team to have had an underwhelming winter. Racing Point -- previously known as Force India -- rarely starts the season well and is expected to bring a major upgrade to one of the early rounds, bolstered by the financial backing of its new owner, Canadian billionaire Lawrence Stroll, father of Sergio Perez's teammate Lance.
Times at close
1. Vettel, Ferrari, 1:16.221, 110 laps (C5)
2. Hamilton, Mercedes, 1:16.224, 61 laps (C5)
3. Bottas, Mercedes, 1:16.561, 71 laps (C5)
4. Hulkenberg, Renault, 1:16.843, 51 laps (C5)
5. Kvyat, Toro Rosso, 1:16.898, 131 laps (C5)
6. Sainz, McLaren, 1:16.913, 134 laps (C5)
7. Grosjean, Haas, 1:17.076, 73 laps (C5)
8. Ricciardo, Renault, 1:17.114, 52 laps (C5)
9. Raikkonen, Alfa Romeo, 1:17.239 (C5)
10. Magnussen, Haas, 1:17.565 (C5)
11. Verstappen, Red Bull, 1:17.709 (C3)
12. Perez, Racing Point, 1:17.791 (C5)
13. Kubica, Williams, 1:18.993 (C5)