Scott Dixon's blistering time of 1:38.7710s set in the Saturday morning session proved the best lap seen so far this weekend from an IndyCar on the 14-turn, 2.983-mile Motegi road course.
And Newman/Haas' James Hinchcliffe's time of 1:39.1074s topped the Saturday afternoon session that was also good enough to stand as second fastest of the weekend so far, seeing off his team mate Oriol Servia and Ganassi's Dario Franchitti in the timesheets.
Dixon's flying lap was set late in the hour-long morning session that commenced at 9am. Will Power had gone top with his first flying lap but then did not improve on that early benchmark until very late on, by which time he had been disposed by Dario Franchitti who topped the times for much of the session until Dixon's flyer in one of the final laps of the morning put the Kiwi 0.3976s clear of the rest.
It was a mixed early session for home favourites, with Hideki Mutoh's early laptime of 1:39.4932s holding up well for the hour, but Takuma Sato ending up the slowest of the 26-car field. His last attempt to improve was thwarted by a minor off-track detour, but he wasn't alone as Franchitti, Ryan Briscoe, Helio Castroneves and James Jakes were among those off-roading at one point or another, as was 2010 Formula Nippon champion Joao Paulo de Oliveira who finished the session in 15th in his IndyCar début weekend.
Scott Dixon also topped the timesheets for much of the later hour's practice as well, but in the final minutes found himself displaced by Newman/Haas duo James Hinchcliffe and Oriol Servia. Hinchcliffe had been the only driver to break up the Penske domination at the top on Friday, and after appearing rather anonymous in the morning practice he was fully on it with a late flier just 0.0339s ahead of Servia late in the session.
The final practice session before Saturday afternoon qualifying saw three brief cautions, the first of the weekend, after spins for HVM's Simona de Silvestro and KV Racing Technology's Tony Kanaan and then a final late stoppage for Ryan Briscoe spinning and stalling. That left the cars with time for only one flying lap after the green flag came out: Hinchcliffe decided to sit out the mad rush back onto the track and his top time held up to the chequered flag.
Qualifying starts at 3pm local time (7am BST) and will consist of a first round split into two groups with the top six from each progressing to round 2, and the top six from that round going out into a pole shootshout.
The groups for qualifying consists of Helio Castroneves, Ryan Briscoe, Alex Tagliani, Joao Paulo de Oliveira, Takuma Sato, JR Hildebrand, Tony Kanaan, Ryan Hunter-Reay, EJ Viso, Charlie Kimball, Graham Rahal, Danica Patrick and Ana Beatriz in Group 1.
Group 2 comprises, Will Power, James Hinchcliffe, Marco Andretti, Dario Franchitti, Sebastien Bourdais, Hideki Mutoh, James Jakes, Scott Dixon, Vitor Meira, Oriol Servia, Giorgio Pantano, Mike Conway and Simona de Silvestro.
Full Saturday practice session times