Phoenix IndyCar test: Helio Castroneves fastest for Penske

Castroneves and Power reeled off laps at 19.5858 seconds (187.850mph) and 19.5931s respectively in the first of Friday's two sessions.

Andretti Autosport Honda driver Marco Andretti had the fastest time of the following night session as he lapped in 19.6038s, just a tick faster than reigning champion Scott Dixon's 19.6066s around the 1.022-mile PIR oval.

"A lot of drivers were running different set-ups - there were more in race trim and not single-lap qualifications [spec] - so we'll get a better idea what it will be like tomorrow," Andretti said.

"It's pretty heavy in between Turns 1 and 2 because the steering gets pretty heavy there.

"You really have to wring the car's neck to get a good time here - that's what I like about it."

A traditional IndyCar venue that first hosted major American single-seater racing in 1964, Phoenix returns to the schedule this year for the first time since 2005.

"It's great to be back here," said Andretti Autosport team owner Michael Andretti.

"I love this place. It's one of my favourite ovals."

Behind the Penske pair in the daytime session, Josef Newgarden was third for Ed Carpenter Racing, ahead of Juan Pablo Montoya in another Penske entry.

Graham Rahal rounded out the top five and was the fastest Honda driver at 19.8501s for Rahal Letterman Lanigan.

ECR was quick again in the evening, when owner/driver Ed Carpenter was third and Newgarden fifth.

They were split by James Hinchcliffe, on his first appearance alongside the full field since his horrific crash in Indianapolis 500 practice last May.

"It feels like the first day back at school," Hinchcliffe said.

"It's competition that you really miss most of all so it's great to be back here with cars on the track."

With Schmidt Peterson driver Hinchcliffe making it two Honda runners in the top four on Friday evening, Michael Andretti was encouraged by the Japanese marque's performance level after Chevrolet's 2015 supremacy.

"It is definitely better and a step in the right direction," Andretti said.

"I think the engine is really good. They made big gains there. It's early, early days but we are cautiously optimistic."

Six more hours of testing is scheduled for Saturday, again split between three hours in the daytime and three under the lights.

AFTERNOON RESULTS:

EVENING RESULTS: