Herta stays top of IndyCar Spring Training with startling lap

At the time, with 67mins of the three-hour session still to run, Herta’s time was an amazing 1.4sec quicker than his nearest opposition.

Team Penske’s Will Power whittled that deficit down to 0.48sec three laps from the end, but then spun coming to the final turn.

"I'm super happy with how the day went," said Herta, 2018 Indy Lights runner-up. "We did some great things to the car and I'm very happy with how the boys got everything together in time for this test.

"Everyone did a fantastic job and there were no issues with the car; it was perfect. We kept chipping away and kept finding time. By the end of the day, we were quickest by quite a margin. I can't wait for tomorrow now."

Power's temporary – and previous – teammate Helio Castroneves in a fourth Penske, was allowed to halt his full-fuel load runs to jump up to third place, albeit 1sec off the ultimate lap from Herta.

Rookie Felix Rosenqvist outpaced Chip Ganassi Racing-Honda teammate by 0.0023sec to grab fourth spot, while Simon Pagenaud made it three Penskes in the top six.

Alexander Rossi was fastest of the Andretti Autosport-Hondas in seventh place, a couple of tenths faster than Graham Rahal who showed major improvement from Rahal Letterman Lanigan Racing’s form at the WeatherTech Raceway Laguna Seca test last Friday.

Dale Coyne Racing’s Santino Ferrucci did a fine job to slot into ninth ahead of Ed Carpenter Racing’s Spencer Pigot who, along with Rosenqvist turned the most laps of the session (38).

Marcus Ericsson and James Hinchcliffe were 11th and 12th for Arrow Schmidt Peterson Motorsports, ahead of Josef Newgarden in the fourth Penske entry.

Ryan Hunter-Reay, who had to have a tow-in early in the three-hour session, narrowly edged teammate Marco Andretti, while RC Enerson was 18th in the faster of the two Carlin-Chevys.

Ed Jones pipped former teammate Bourdais to ninth, while Kyle Kaiser’s Juncos Racing entry was 24th, 3.25sec off Herta’s pace after missing the morning session.

Tony Kanaan’s AJ Foyt Racing-Chevy lunched its gearbox, so he only completed six laps.

Testing times: