Andretti Autosport's Marco Andretti was fast right from the beginning of the first 45-minute practice session at Iowa Speedway, ultimately topping the timesheets with a lap of 17.4126s (184.832mph).
That put him 0.0332s ahead of Sarah Fisher Hartman Racing rookie Josef Newgarden, with Alex Tagliani and Ryan Briscoe close behind and within seven hundredths of a second of Andretti's best time on the 0.875-mile asphalt tri-oval.
The top 20 drivers were all running faster than 2011 pole speed, which was 180.373mph. The gap between first and 24th was only 0.6682s, with only HVM's Simona de Silvestro falling outside the one second margin.
There were no issues or red flags during the 45-minute session, although Scott Dixon lost time in practice with a suspected fuel pump pressure issue. The Ganassi team seemed content that the problem had been resolved and Dixon was able to set the fifth fastest time of the morning.
Practice 1 is the only time the teams have this weekend to run set-up tests without having to worry about qualifying. In a late tweak to the experimental 'heats' format for Iowa that will set the starting grid for Saturday night's race, IndyCar decided not to include practice 1 times in establishing the groups for this evening's three heat races, and will instead take the order at the end of the second 45-minute practice session later today.
The first of the three 30-lap qualifying heats will consist of those cars from tenth position down in the even number positions at the end of practice 2; the order at the end of the 30-lap heat race then sets positions tenth, 12th, 14th etc on the grid for the Iowa Corn Indy 250.
The second heat will consist of those cars in the odd-numbered positions in practice 2 from ninth place down with the order finalising those positions (ninth, 11th, 13th, etc.) on the starting grid., and the third heat will consist of the remaining top eight cars from the practice sessions, and the order at the end of the 30-laps will set the front four rows of the grid for the main race itself.
Earlier in the week, it was confirmed that KV Racing Technology duo Tony Kanaan and EJ Viso would have ten-place starting grid penalties for Iowa wherever they end up qualifying under the one-off system, after both cars needed new Chevrolet engines following last eekend at Milwaukee.
IndyCar has also further modified the aerodynamic rules for Iowa, imposing a maximum rear flap angle of 37 degrees and mandating that no rear wickers or gurney flaps are allowed, which will reduce available downforce by almost a tenth.
Race control have also modified their own internal procedures following the embarrassing gaffe wrongly penalising Scott Dixon last weekend: in future, special camera footage of the starter will be used to synchronise replay footage to ensure there are no further synchronisation issues and that it's clear when a restart has proceeded.
Full practice 1 times