Espargaro rectifies past mistakes to set pace at Catalunya MotoGP
The Aprilia rider was fastest in both the day's sessions with fellow Catalan and teammate Maverick Vinales second both times.
Francesco Bagnaia, the reigning world champion and runaway leader this season, was third in the afternoon on his Ducati.
Last year, Espargaro, born a few kilometres down the road from the Montmelo track, was the quickest in every session ahead of the race.
He set off from pole and was running second to Frenchman Fabio Quartararo, when his local knowledge let him down.
Espargaro celebrated a podium finish a lap early, waving and slowing. By the time he realised his mistake, three riders had passed. He eventually finished a sheepish fifth.
On Friday, with the slogan "One more lap" painted on his helmet, he started to make amends.
In the morning, Espargaro was 0.264sec faster than Vinales. In the afternoon, he trimmed more than a second off his best morning time with a track record of 1 min 38.686sec to outpace Vinales by 0.362sec.
Bagnaia was third in the afternoon on a factory Ducati another 0.013sec back. He was followed by Johann Zarco on a Pramac Ducati, Brad Binder on a KTM and Alex Marquez on a Gresini Ducati.
"It's not about revenge," said Espargaro.
"I did a big mistake last year. At the beginning it was really difficult to get past and keep going. At the end it's a mistake - as a human I make a lot of mistakes. It was a big one last year."
He said it was a mistake he would not repeat.
"The marshals have to be careful because when I see the chequered flag I will keep going for one more lap."
Younger brother Pol Espargaro was sixth on Friday on a KTM. Italian Marco Bezzecchi, who is third in the standings, was seventh on a Mooney Ducati.
Jorge Martin, a distant second to Bagnaia in the standings, was 10th on the second Pramac.