Alex Palou completed 43 laps in IndyCar’s new IR28 chassis at Sebring International Raceway on Monday before a fuel-system problem ended his test day. The run was the car’s first test outside Indianapolis Motor Speedway and Palou’s fourth day evaluating it. The engineering crew could not get the car running again. Palou said the team had already logged substantial mileage that morning and described Sebring’s bumpy, rough surface as a demanding test ahead of work on street circuits. Monday’s session also brought the IR28 onto the track at the same time as the current DW12 chassis for the first time. Andretti Global’s Kyle Kirkwood and Team Penske’s Scott McLaughlin were at Sebring testing Firestone tires in DW12 cars. Palou later shared the track with Kirkwood for several laps. He said Kirkwood had fresher tires, while noting that the new car allowed him to brake deeper. IndyCar and Dallara are using the early sessions to validate the IR28, with drivers providing feedback rather than chasing speed. Palou, who races for Chip Ganassi Racing, is testing the car after being selected by Honda; Alexander Rossi of Ed Carpenter Racing, selected by Chevrolet, was scheduled to drive it Tuesday. Palou also praised changes to the cockpit and cooling system, saying airflow was strong even in Sebring’s warm, humid conditions. Testing is set to continue this fall as Chevrolet and Honda work toward completing regulations for the series’ new 2.4-liter twin-turbocharged V6 engine.