Robin Frijns was the first of the runners to start with a representative time in the 1m23s, but the times quickly wound down to yesterday's ballpark - with a flurry of runners quickly getting into the 1m22s boundary.
Jake Dennis then broke into the lower bracket with his 1m21.905s after the halfway mark, but Andre Lotterer - set to depart the Porsche Formula E squad at the end of the year - eclipsed the Briton with a 1m21.811s. Wehrlein then joined him in the top two with a 1m21.836s.
Dennis and Antonio Felix da Costa then vaulted to the top, setting a 1m21.432s and 1m21.430s respectively, before Edoardo Mortara beat the pair by 0.08s.
The session was effectively nullified two-thirds of the way in, as a full-course yellow was called for the stranded Avalanche Andretti of Oliver Askew. The American had come to a stop on the exit of the stadium section, and had to be brushed into the service road to get the session running once more.
Although Evans looked to be in contention for top spot, a snatched brake at Turn 22 nibbled away at his time advantage and deprived him of a chance to usurp Mortara.
The Swiss driver then bettered his lap, punching in a 1m21.019s while dancing very close to the Seoul barriers, as Dennis' follow-up of a 1m21.352s was over three tenths away.
Da Costa then grabbed second at the chequered flag to beat Dennis, but could not bridge the gap to Mortara - who looked more confident after ending Saturday's running noticeably downbeat after retiring with a puncture.
Evans' lap kept him in fourth ahead of Lucas di Grassi, as champion-elect Stoffel Vandoorne was sixth fastest ahead of Frijns.
Lotterer was eighth with Nick Cassidy ninth, while NIO 333's Oliver Turvey once again found the top 10 in a Seoul practice session.
Antonio Giovinazzi was ruled out of the season finale in South Korea with a hand injury, and thus Jaguar reserve Sacha Fenestraz will cover for him in Sunday's race.
Fenestraz, armed without Saturday's knowledge of the circuit, had to learn quickly and build up speed over the course of the session - notably brushing the Turn 22 exit barrier but sustained no damage to his Dragon.
The Franco-Argentine driver grabbed a 1m23.028s on his final lap of the session, bringing him to within 0.035s of Maximilian Guenther in 21st.
