Updated: Andretti holds spot after second practice session at Iowa Speedway

NEWTON, Iowa - The field couldn't keep up with Marco Andretti.

Andretti was the lone driver to surpass 186 miles per hour during the second practice session of the IZOD IndyCar Series Iowa Corn Indy 250 Friday at Iowa Speedway. Andretti recorded a fastest lap of 186.041 to earn the lead spot in the third qualifying heat race later Friday. The heat will determine the pole sitter and top-eight order in Saturday's race that starts at 9 p.m.

Dario Franchitti, who won the Iowa Corn 250 in 2007 and 2009, bolted to a 185.715 lap in the final minute of practice to move into second.

The next three fastest cars were all Team Penske drivers. Helio Castroneves, Will Power, the season points leader, and Ryan Briscoe are third through fifth.

Andretti's Andretti Autosport teammates James Hinchcliffe, who is second in season points trailing Power by 31, and Ryan Hunter-Reay, who won last week at the Milwaukee IndyFest, were sixth and seventh. Scott Dixon was eighth.

The IZOD IndyCar Series instituted heat races to race qualifying instead of two-lap, single-car qualifying. Fields of the three heat races will be determined by performances in the two practice sessions. The top eight will race in one determining the top eight starting positions for the race Saturday night at 9. The drivers in odd positions, starting at ninth and through the remainder of the field will compete for spots nine, 11, 13, 15, 17, 19, 21, 23 and 25. Drivers in even positions after practice will run in a heat for places 10, 12, 14, 16, 18, 20, 22 and 24.

The race fields include:

Heat one (Evens 10-24) - Graham Rahal*, Josef Newgarden, E.J. Viso, J.R. Hildebrand, Oriol Servia, Mike Conway, Ed Carpenter, Takuma Sato

Heat two (Odds 9-25) - Rubens Barrichello, Alex Tagliani, Justin Wilson, Tony Kanaan*, James Jakes, Charlie Kimball, Simon Pagenaud, Katherine Legge, Simona de Silvestro

Heat three (Top eight) - Marco Andretti, Dario Franchitti, Helio Castroneves, Will Power, Ryan Briscoe, James Hinchcliffe, Ryan Hunter-Reay, Scott Dixon

*-10-spot grid penalty.