The Citroen racer's effort of 1m23.101s was 2.6 seconds inside team-mate Yvan Muller's 2013 qualifying lap record, set in a S2000 spec' Chevrolet Cruze.
Campos Chevrolet driver Hugo Valente ended just 0.027s adrift of Lopez's benchmark to repeat his Slovakia-Ring test and practice session position.
Top honours among the four-car Honda contingent fell to Mehdi Bennani in third. The Proteam driver, who has been sidelined from qualifying in the two previous meetings owing to turbo-related issues, edged out reigning WTCC champion Muller by 0.031s.
The test was red-flagged with a little over three minutes of its scheduled half-hour remaining, when Tom Coronel and Gabriele Tarquini parked up on the back straight.
Earlier in his lap, Coronel had gone straight at the Turn 1 chicane after suffering a punctured front tyre. Tarquini stopped his factory JAS Honda directly behind Coronel's ROAL Cruze, before opening his bonnet to investigate a possible power-steering failure.
The subsequent abandonment of the session secured Lopez's position at the top of the timing screens.
The former TC2000 champion had deposed Bennani at the head of the classification at the two-third mark. The initial pace was set by Muller, thanks to a strong lap of 1m23.281s from cold.
Tarquini's team-mate Tiago Monteiro ended the day fifth, ahead of nine-time World Rally champion Sebastien Loeb.
Hungaroring reversed-grid winner Gianni Morbidelli was the fastest runner in the second sector en route to seventh.
The session took place under overcast skies, and rain is forecast prior to qualifying on Saturday afternoon.
Pos Driver Car Time Gap Laps 1. Jose Maria Lopez Citroen 1m23.101s 15 2. Hugo Valente Campos Chevrolet 1m23.128s +0.027s 12 3. Mehdi Bennani Proteam Honda 1m23.250s +0.149s 15 4. Yvan Muller Citroen 1m23.281s +0.180s 16 5. Tiago Monteiro Honda 1m23.476s +0.375s 13 6. Sebastien Loeb Citroen 1m23.513s +0.412s 14 7. Gianni Morbidelli Munnich Chevrolet 1m23.672s +0.571s 13 8. Norbert Michelisz Zengo Honda 1m23.784s +0.683s 13 9. Tom Chilton ROAL Chevrolet 1m23.811s +0.710s 10 10. Tom Coronel ROAL Chevrolet 1m23.831s +0.730s 11 11. Gabriele Tarquini Honda 1m24.030s +0.929s 12 12. Rene Munnich Munnich Chevrolet 1m24.606s +1.505s 14 13. Dusan Borkovic Campos Chevrolet 1m24.683s +1.582s 9 14. Rob Huff Lada 1m25.002s +1.901s 11 15. James Thompson Lada 1m25.323s +2.222s 8 16. Mikhail Kozlovskiy Lada 1m25.668s +2.567s 14 17. Franz Engstler Engstler BMW 1m27.501s +4.400s 14 18. Pasquale di Sabatino Engstler BMW 1m28.829s +5.728s 14 19. John Filippi Campos SEAT 1m30.482s +7.381s 11
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