Daniel Ricciardo ended Formula 1's young driver test at Jerez in scintillating form as the Red Bull driver recorded the fastest time of the week to sit on top of the timesheets.
The Australian completed 77 laps of the Spanish circuit and set the pace in a time of 1m17.418s.
It was not all plain sailing for the British F3 champion though, as his day's work was ended early when a large plume of smoke appeared from the back of his car and he stopped at the exit of the chicane, bringing the session to a halt.
Britain's Paul di Resta continued his impressive week of testing with the second quickest time for Force India. He also had his problems during his half-day of running.
A spin into the gravel at the chicane early in the afternoon brought the red flags out, as did an incident 90 minutes later when his car cut out at the same point while the DTM driver was on an out-lap.
Wednesday pace-setter Gary Paffett and Mike Conway were third and fourth quickest for McLaren and Brawn respectively. Both had half a day behind the wheel.
Nico Hulkenberg's Williams and Bertrand Baguette's Sauber were behind them, the Belgian driver improving his best time on a number of occasions in the final hour.
Brit Oliver Turvey was an impressive third quickest in the morning running with McLaren, but was pushed down the order to seventh by the end of the day as conditions improved.
Brawn's Marcus Ericsson, Renault's Lucas di Grassi and Force India's JR Hildebrand completed the top 10, although the American's two runs on his best sets of tyres were spoiled by issues with the car's electronics.
Ferrari gave maiden runs to the top three finishers in this year's Italian F3 Championship. Mexican Pablo Sanchez, the last to venture onto the circuit, was the fastest of them in 11th place. The first out, Daniel Zampieri, was also the first to bring out the red flags as he spun into the gravel at the chicane early on.
Toro Rosso made a late decision to allow Mirko Bortolotti to drive in the morning before he handed the car over to Brendon Hartley.
Pos Driver Team Time Laps 1. Ricciardo Red Bull 1m17.418s 77 2. Di Resta Force India 1m18.736s + 1.318s 53 3. Paffett McLaren 1m18.746s + 1.328s 59 4. Conway Brawn 1m19.096s + 1.678s 77 5. Hulkenberg Williams 1m19.226s + 1.808s 106 6. Baguette Sauber 1m19.356s + 1.938s 70 7. Turvey McLaren 1m19.358s + 1.940s 32 8. Ericsson Brawn 1m19.382s + 1.964s 49 9. Di Grassi Renault 1m19.602s + 2.184s 123 10. Hildebrand Force India 1m19.873s + 2.455s 41 11. Sanchez Ferrari 1m21.147s + 3.650s 39 12. Zampieri Ferrari 1m21.279s + 3.861s 42 12. Zipoli Ferrari 1m21.725s + 4.307s 41 13. Hartley Toro Rosso 1m22.493s + 5.075s 50 15. Bortolotti Toro Rosso 1m23.271s + 5.853s 34 16. Tung Renault 1m32.477s + 15.059s 4 All Timing Unofficial