Kimi Raikkonen set the pace on the final day at Jerez during which a disintegrating kerb caused a midday stoppage.
Friday's running began in a fiery fashion as, after just two laps in the new Ferrari F138, Pedro de la Rosa had to leap from the car after it caught fire.
The marshals were quickly on the scene and put out the flames which were reportedly caused by a gearbox malfunction.
With the track again green, Sebastian Vettel was the first to slide under the 1:19 barrier before Sauber's Esteban Gutierrez topped his time.
Vettel, though, returned to the front shortly after on a soft tyre run and was leading the way with a 1:18.565 when a hole in a kerb brought proceedings to a halt.
The red flags were out for almost a full hour as track worked sought different way to repair the damage to the kerb at Turn 9 before finally bringing out the cement.
With the action back underway the drivers ventured and were soon joined by de la Rosa in his repaired Ferrari.
Force India hopeful Jules Bianchi, who has yet to learn whether or not he'll race for the team this season, was the first to lower the benchmark time as he posted a 1:18.175.
Bianchi's time, though, was edged by Kimi Raikkonen when - with an hour to go - the Lotus driver went 0.027s quicker.
Although not quicker than the week's best of 1:17.879, which was set by Felipe Massa on Thursday, Raikkonen's time proved to the second quickest of the four-day test.
Vettel finished in third place, 0.417s down, while Sauber rookie Gutierrez was fourth ahead of Jean-Eric Vergne who put in a very late charge to move up the order.
Mercedes driver Lewis Hamilton had a much better day in the W04 as he amassed 145 laps with a best time of 1:18.905.
His McLaren replacement Sergio Perez was seventh quickest, finishing ahead of Valtteri Bottas, who was the only driver in an old 2012 car.
01. Kimi Raikkonen Lotus 1m18.148 82 laps
02. Jules Bianchi Force India 1m18.175 + 0.027 56 laps
03. Sebastian Vettel Red Bull 1m18.565 + 0.417 96 laps
04. Esteban Gutierrez Sauber 1m18.669 + 0.521 142 laps
05. Jean-Eric Vergne Toro Rosso 1m18.760 + 0.612 92 laps
06. Lewis Hamilton Mercedes 1m18.905 + 0.757 145 laps
07. Sergio Perez McLaren 1m18.944 + 0.796 97 laps
08. Valtteri Bottas Williams 1m19.851 + 1.703 91 laps
09. Pedro de la Rosa Ferrari 1m20.316 + 2.168 50 laps
10. Charles Pic Caterham 1m21.105 + 2.957 109 laps
11. Luiz Razia Marussia 1m21.226 + 3.078 81 laps
12. Paul di Resta Force India 1m23.435 + 5.287 49 laps
Jerez Day Four in pictures