Mercedes hit by hydraulics problem as Verstappen impresses
Verstappen was not top of the timesheets but Alfa Romeo's Zhou Guanyu (23), who led the second session with the fastest lap yet, was on the much softer C5 tyres compared to the Dutch driver's C3s.
"Today we focused on the smaller details and took little steps," said Verstappen, who hands over to Mexican Sergio Perez (33) for Saturday's final day.
"Again, the car was responding well to everything we did... I’m very pleased with the testing period, every time I jumped in the car I felt comfortable and could push instantly.
"We’ll have to see how quick we will be next week but I’m feeling positive."
George Russell (25) brought out red flags when he stopped on track, his Mercedes stuck in fourth gear, with some 90 minutes remaining.
The car was recovered and did not go back out.
Russell had already told reporters that the team were struggling a little with the car's balance and said it would be a bit of a stretch to expect Mercedes to be challenging for victory in next weekend's opener.
The Briton ended the day 13th of 17 drivers on track with seven time world champion teammate Lewis Hamilton (38), who went out in the morning, 15th.
Mercedes boss Toto Wolff (51) told Sky Sports television, however, that the former champions were 'hiding' their true pace.
Verstappen set his time of one minute 31.650 seconds in the afternoon, before Zhou went 0.040 quicker in cooler evening conditions.
Spain's double world champion Fernando Alonso (41) was third fastest for Aston Martin, with that team looking seriously quick with a car designed under former Red Bull aerodynamics head Dan Fallows.
Alonso did a hefty 130 laps, with race team mate Lance Stroll (24) ruled out of the test after suffering a cycle injury while training in Spain.
Ferrari's Carlos Sainz (28) was fastest in the morning, before teammate Charles Leclerc (25) took over in the afternoon.
"It’s been another positive day. Reliability was again very good and we've been able to explore all the set-ups we targeted to test," said the Spaniard.
"We keep exploring the limits of the car and finding potential areas where we can maximise performance. The main target is to keep up the good work tomorrow and get ready for next week."
American rookie Logan Sargeant (22) was second fastest for Williams in the morning and perhaps more impressively did a mighty 154 laps over the day, more than anyone else.
