The #2 Chevy set a chart-topping 225.687mph lap to lead front-row starter Takuma Sato in the #75 Honda for Rahal Letterman Lanigan Racing on a 225.415mph best.

Sato’s session wasn’t entirely trouble-free. He slowed late in the session to bring out the last of three stoppages.

“I would say we weren’t entirely happy with (car setup) yet, but we were making good progress,” Sato said.

“We were pointing in the right direction, so I want to check all the data.

“We had a mechanical failure on the last run and lost performance on one side of the car.

“It’s too early for me to say what that was until the team investigates it, but I almost lost control in Turn 1, and we are just fortunate I didn’t hit anything.”

Scott Dixon was third for Chip Ganassi Racing, clocking a session-best 225.200mph lap on just his sixth lap in the #9 Honda.

“Good final run here,” Newgarden said, who will start the Indianapolis 500 from 32nd.

“Excited to check the car off again and work with the team.

“I’m really excited for Sunday. The main show. Everything we work for.”

The two-hour practice acted as something of a warm-um to the Greatest Spectacle In Racing. For sure, it got a little too warm.

Rahal Letterman Lanigan Racing’s Graham Rahal brought practice to a halt when smoke began to pour from his car.

That team was forced to make an engine change in the wake of the failure, meaning they will go into the race without any practice running on that motor.

Ryan Hunter-Reay’s sessions came to a spectacular end when fuel began to leak from his car.

The Dreyer & Reinbold Racing driver said he felt something wet in his race suit before smoke began to pour into the cockpit.

Hunter-Reay, who won the 2014 Indianapolis 500, leapt from his car as flames licked the engine cover.

“I just felt a lot of liquid on my left side and it must be because of the ambient too, but it just felt really cold,” said Hunter-Reay.

“Your first [thought] is fuel. I had a methanol fire back in 2003 and I just remember what went on there and that same kind of feeling.

“After I felt the liquid or whatever it was. It could have been some type of fire retardant liquid, but it just started smoking more and more and more.

“I just tried to keep air speed up to get back to this side of the track where there’s more help.

“I thought, I don’t just want to pit, stop in my box where we have all these people without suits on, so I decided [to park] up there. Then I looked like Ace Ventura trying to come out of the rhino.

“Got out, no big fire. It didn’t look like it caused a lot of damage but I lost the ability to shift, downshift. I lost the ability to turn the car off.

“That’s a bummer. I have no idea. I hope it’s not a hybrid deal because Jack [Harvey] earlier in the week had a hybrid meltdown on him.

“That caught my attention. When it started going up in smoke when you’re in fourth gear, that’s when you know something is going seriously wrong.”

Hunter-Reay said the team would investigate what caused the fire.

“They said they saw fire leaving, which is kind of common sometimes,” Hunter-Reay explained.

“We had just filled with fuel. As you can see, we had stickers (new tyres) on the car.

“We had just filled the car, so we were hoping that that was just going to put itself out with just some residual fuel on the sidepod.”

The 109th Running of the Indianapolis 500 gets underway on Monday, May 25 at 2:45am AEST with coverage live and exclusively on Stan Sport in Australia.

Results: 109th Indianapolis 500, Carb Day Practice