A race winner in the series and Champ Car, Wilson split with Dale Coyne Racing at the end of the 2014 season, and has only made a pair of starts this year.

Both of those came with Andretti in May, on the Indianapolis road course and oval, while he also raced with the team’s Formula E outfit in Moscow last month.

Wilson will take over Andretti’s #25 entry – also driven on occasion this year by Simona de Silvestro – for the remaining five events.

“I’m really looking forward to making the most of these five races, and just trying to help the team and Honda as much as I can and try and be successful,” he said.

“It’s not going to be easy jumping in towards the end of the year – everyone’s worked out what they’re looking for from the car and the aero kits.

“But I think it puts us in good shape for learning things and trying to progress… and hopefully to set something up towards next year.

“We’ll have to take it one step at a time, but the great thing with IndyCar racing is any weekend anyone can win.

“You just have to make sure you do a good job and do everything as perfect as you can, and that will lead to good results.”

Wilson was due to tackle the Pikes Peak hillclimb in an HPD LMP2 car last month, but mechanical problems curtailed the programme before the event.