The IZOD IndyCar Series teams have completed their all-important second practice that will designate lineups for the three heat race scheduled later this evening. Those three races will determine the grid for Saturday night's Iowa Corn 250 on the 0.875-mile Iowa Speedway oval, the third consecutive oval race in as many weekends.

As he did during the first practice, Marco Andretti was the quickest driver of the day. The (newly clean-shaven) defending race winner at this track, Andretti took his No. 26 Andretti Autosport Team RC Cola Dallara/Chevrolet/Firestone Indy car used his eighth lap of 43 to put up a massive 186.041-mph tour of the oval. It took Dario Franchitti until his penultimate (of 57) lap to bring the No. 10 Team Target Honda-powered Indy car to second overall, at 185.715.

Team Penske's Helio Castroneves was third in the No. 3 Penske Truck Rental Chevy at 185.713, zooming up the speed charts early in the afternoon to take that time on his fifth lap. Teammate Will Power was fourth in the No. 12 Verizon Chevy at 185.512 and the third Penske driver, Ryan Briscoe was fifth in his No. 2 PPG Automotive Finishes Chevy.

James Hinchcliffe's No. 27 Chevy took sixth place, last weekend's winner, Ryan Hunter-Reay was seventh with his No. 28 DHL/Sun Drop Chevy and Scott Dixon took the final spot for the third, pole-shootout heat race with the No. 9 Target Honda, giving Honda and Chip Ganassi Racing two spots in the oval equivalent to Firestone Fast Six qualifying.

Nearly all the drivers said the Firestone tires go off after about 20 laps, so we might expect the three, 30-lap heat races to come alive in the final 10 tours of this fun oval. With 25 cars on the premises, the balance of the field is delegated for their heats by even and odd-numbered finishes in this practice session.

From ninth place onward, the odd-numbered drivers in their second heat race are: Rubens Barrichello (Chevy), Alex Tagliani (Honda), Justin Wilson (Honda), Tony Kanaan (Chevy), James Jakes (Honda), Charlie Kimball (Honda), rookie Simon Pagenaud (Honda), rookie Katherine Legge for Chevy and Simona de Silvestro's Lotus, the sole car more than a second behind Andretti at 175.269 mph.

From tenth back in the first heat race lie Graham Rahal (Honda), rookie Josef Newgarden (Honda), EJ Viso's Chevy, JR Hildebrand's Chevy, Oriol Servia (Chevy), Mike Conway (Honda) , Ed Carpenter (Chevy) and Takuma Sato's Honda.

The three heat races that determine Saturday's Iowa Corn 250 grid take place later Friday evening and will be shown on NBC Sports beginning at 8PM EDT on Saturday, with the race following immediately afterwards.