Scott Dixon improved upon the fastest lap from Friday’two sessions late in the Saturday morning outing but was overcome by Graham Rahal who reduced the mark further to a 1:07.1866.
The final lap turned by reigning Long Beach winner Rossi was completed after the appearance of the checkered flag but was 0.1278 seconds faster than the best from Rahal, who had already returned to his pit box. In 1:07.0588, Rossi’s lap was a significant 0.7352 seconds quicker than the one that made Dixon fastest on Friday.
Ryan Hunter-Reay added a second Andretti-prepared Honda to the top five, 0.3444 seconds quicker on his very best tour of the 1.968-mile temporary street circuit than Simon Pagenaud, who placed fifth.
Honda held a 6-4 edge in the group, which lapped within 0.4673 seconds.
Sebastien Bourdais and James Hinchcliffe at 11th and 12th came within half a second of Rossi’s leading time while Matheus Leist, having ventured into runoff areas double, brought up the rear of the 23-car field at 1.1104 seconds off the pace. All 23 drivers set their best times of the weekend during Practice 3.
Qualifying for the Acura Grand Prix of Long Beach is next for IndyCar in Southern California. The grid will be set starting at 12:10 p.m. Saturday with live television coverage on NBCSN.