Pocono IndyCar: Marco Andretti leads pre-race test day

Andretti set the pace with a 220.963mph lap during the afternoon session of the test, which was aimed at allowing teams a chance to work with the revised aero and tyre package that will be utilised this weekend.

"I think this just became my favourite racetrack," said Andretti. "It's so different every lap, and that's the fun about it. You don't know what to expect. You have to really be on the tools end-to-end and chase the car. I think it's going to produce a heck of a race."

Indianapolis 500 winner Tony Kanaan, who will remain in contention for the reintroduced Triple Crown if he can win on Sunday, was second-fastest ahead of points leader Helio Castroneves.

Kanaan was among the drivers who also tested at the Pennsylvanian track last week, and said that the unique layout meant that those who had run on the circuit prior to Thursday's test were at an advantage.

"We used last week's test for the things I call the big things," he said. "Things that will take a long time to change. I can't get into much detail, but they're changes in the car that will sometimes take a couple hours for you to figure out. It was definitely helpful."

IndyCar has made a late change to its aero specification for the weekend, with the teams now having the option to run an underwing strake to create more downforce.

Firestone, meanwhile, used the day to test solutions to track-specific tyre wear problems that were detected last week.

Cars will now run Indianapolis-spec tyres on the left of the car, and more durable Texas-spec tyres on the right side for Sunday's race.

Pos  Driver               Team/Engine      Time      Gap
 1.  Marco Andretti       Andretti/Chevy   40.7308s
 2.  Tony Kanaan          KV/Chevy         40.9460s  +0.2152s
 3.  Helio Castroneves    Penske/Chevy     41.0729s  +0.3421s
 4.  Ed Carpenter         Carpenter/Chevy  41.1357s  +0.4049s
 5.  Ryan Hunter-Reay     Andretti/Chevy   41.2290s  +0.4982s
 6.  Scott Dixon          Ganassi/Honda    41.2425s  +0.5117s
 7.  Sebastien Bourdais   Dragon/Chevy     41.2448s  +0.5140s
 8.  James Hinchcliffe    Andretti/Chevy   41.2484s  +0.5176s
 9.  Will Power           Penske/Chevy     41.2521s  +0.5213s
10.  James Jakes          Rahal/Honda      41.3221s  +0.5913s
11.  Simon Pagenaud       Schmidt/Honda    41.3280s  +0.5972s
12.  Charlie Kimball      Ganassi/Honda    41.3330s  +0.6022s
13.  Justin Wilson        Coyne/Honda      41.3594s  +0.6286s
14.  Ryan Briscoe         Panther/Chevy    41.3742s  +0.6434s
15.  Dario Franchitti     Ganassi/Honda    41.3757s  +0.6449s
16.  Alex Tagliani        Herta/Honda      41.3794s  +0.6486s
17.  Josef Newgarden      Fisher/Honda     41.4211s  +0.6903s
18.  EJ Viso              Andretti/Chevy   41.4274s  +0.6966s
19.  Takuma Sato          Foyt/Honda       41.4386s  +0.7078s
20.  Tristan Vautier      Schmidt/Honda    41.5274s  +0.7966s
21.  Simona de Silvestro  KV/Chevy         41.7007s  +0.9699s
22.  Graham Rahal         Rahal/Honda      41.7654s  +1.0346s
23.  Pippa Mann           Coyne/Honda      41.7928s  +1.0620s
24.  Sebastian Saavedra   Dragon/Chevy     41.8603s  +1.1295s

All drivers use Dallara DW12 chassis