DS Techeetah driver Antonio Felix da Costa, who will likely win the Formula E title this afternoon, went quickest in Sunday practice on the conventional Berlin circuit.
If the Portuguese driver wins the E-Prix at the Tempelhof Airport later today, he will be guaranteed of the 2019-20 championship.
Similarly, carrying a 68-point lead over Maximilian Guenther, all da Costa needs to do is finish the race with a 60-point advantage to seal the crown.
He came out of the blocks fastest in the single 45-minute practice session, topping the leader board with a late full-power run to supersede nearest rival Guenther by 0.039s.
A tame practice run was led by Venturi driver Edoardo Mortara for much of the opening half as drivers circulated in a standard 200kW powertrain setting.
But as they escalated through the 235kW attack mode and then 250kW full-power map late on, it was Envision Virgin Racing duo Sam Bird and Robin Frijns who led the way - despite a Turn 10 lock-up for Frijns and Bird complaining of first-corner understeer.
They were joined by Audi factory driver Rene Rast to complete a provisional top three lock-out for the e-tron FE06 powertrain.
But then Dragon Racing's Nico Muller became the first person to switch to full power mode, which put him top of the times on a 1m06.666s with eight minutes to go.
Once again the Penske EV-4 showed promising one-lap pace, which has so far not carried through for drivers Muller and Sergio Sette Camara in the races.
Reigning FIA Formula 2 champion Nyck de Vries posted the fastest first two sectors to depose Muller by 0.109, but he too was quickly replaced by Mercedes team-mate Stoffel Vandoorne.
Although his title hopes took a dash in the Saturday race when he retired followed a puncture, Vandoorne bounced back with a decent 1m06.474s.
In a fight for bragging rights on home soil in the German capital city, BMW Andretti driver Guenther then ran to first place by a 0.116s.
Da Costa twice endured large brake lock-ups in the session, first over the bump into Turn 6 and then into the Turn 9 hairpin.
But he recovered well to end the session with an unmatched 1m06.319s.
Nissan e.dams driver Oliver Rowland slotted in third behind Guenther, leading Vandoorne and with Sebastien Buemi a solid fifth in front of de Vries.
Jaguar's Mitch Evans - who showed promising fastest-lap pace in the preceding day's race - ran to seventh ahead of reigning champion and Berlin race three polesitter Jean-Eric Vergne.
Sam Bird held off the advances of Lucas di Grassi for ninth, with Muller dropping to an eventual 11th.
Berlin E-Prix IV practice results
|1||Antonio Felix da Costa||DS Techeetah||DS||1m06.319s|
|3||Oliver Rowland||Nissan e.dams||Nissan||0.131s|
|5||Sebastien Buemi||Nissan e.dams||Nissan||0.218s|
|6||Nyck de Vries||Mercedes||Mercedes||0.238s|
|8||Jean-Eric Vergne||DS Techeetah||DS||0.305s|
|10||Lucas di Grassi||Audi||Audi||0.337s|
|15||Sergio Sette Camara||Dragon||Penske||0.531s|