In unexpectedly dry conditions, Lopez was fastest on his first run and, after a red-flag period to clear a stricken European Touring Car Cup car, bettered that effort by five seconds on his second run as he recorded a time of 8m38.229s in his Citroen C-Elysee.
But the Argentinian went even quicker on his final run, smashing the previous lap record by 1.9 seconds with an effort of 8m35.541s.
"I found the confidence in the last few runs," said Lopez. "This is teamwork, not just me.
"I had the confidence because I was in P1 to try and push more. With low fuel in the end it was a fantastic."
Team-mate Yvan Muller wound up second quickest, but found himself 3.573s down on Lopez's time in his C-Elysee.
Tom Coronel was a fine third, a further second back from Muller, while Norbert Michelisz was fourth and fastest of the three factory Honda cars.
Tom Chilton's strong form translated into fifth on the grid for Sunday's main race, with Thed Bjork a surprise sixth - with both he and team-mate Fredrik Ekblom having opted to focus on race set-up over single lap pace for the majority of the weekend.
Rob Huff was seventh in the second Honda Civic - although he will take a penalty after a crash in first practice on Sunday evening wrecked his original engine.
Nicky Catsburg was seventh and the fastest of Lada's contingent, with Mehdi Bennani and Huff's team-mate Tiago Monteiro completing the top 10 - putting the Honda driver on race one pole with the reverse grid.
Aside from the mid-session stoppage, there was one incident of note as Lada's Hugo Valente crashed towards the end of his second lap of the 14-mile circuit.
In-car footage and audio suggested that Valente had a mechanical issue and lost control of his car through the fast Antoniusbuche curves at the end of the Dottinger Hohe straight, spinning through the Tiergarten curve and smacking the barrier before stoping at Hohenrain.
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