Josef Newgarden was top of the timesheets at the end of Saturday, and he duly carried on in similar fashion with the fastest time of the final 45-minute practice session on Sunday morning as well.
The CFH Racing driver once again left it late before posting a lap of 21.4117s (170.654mph) just before the end of the session, putting him 0.0385s ahead of Penske's Helio Castroneves ahead of qualifying for the Milwaukee IndyFest 250, the 12th round of the 2015 Verizon IndyCar Series championship.
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"The Direct Supply car has been fast," said the 24-year-old from Tennessee, who finished in the top five here 12 months ago. "It was fast here last year, so I expected us to be on our game. I think we have a great spot to start. We just need to keep it up.
"It always helps when you roll off the truck good. I don't know how many guys did [qualifying] sims, but we did one at the end. It's pretty representative of a speed we can do. Hopefully that's going to be enough to stay ahead of everyone else."
His Sunday morning pace improves on the time Newgarden set on Saturday which came in at 21.5414s (169.626mph), which was already faster than last year's pole-winning time recorded by Penske's Will Power with a two-lap average speed of 169.262mph. Newgarden's time today was 5mph faster than the pace set in the equivalent session last year that was achieved by James Hinchcliffe.
It's an important race for Castroneves, who is at risk of losing touch in the championship battle. He's currently in fifth place, 77 points behind his team mate Juan Pablo Montoya.
"Obviously we've been up and down," Castroneves said. "Last race in Fontana was not the result we wanted. We had a very, very strong car. We want to make that this championship stay in the hands of Team Penske. We're going to do anything we can to make that happen.
"When you achieve a good result in a tough place like Milwaukee, it's great," added the Brazilian racer. "Because you don't have the banking, you got to drive the car. The car's not going to be perfect most of the times. At one point it might be great. Another part of the track it might be a disaster. To combine both, you got to hit the limit."
While the top two spots went to Chevrolet-powered teams, the Honda contingent is also continuing to hold its own here this weekend. Graham Rahal was the fastest representative from the Japanese marque and was third fastest in the Rahal Letterman Lanigan #15 just 0.0878s off Newgarden's top time.
"Right away the balance of the car was really good. I was definitely pleased with it," said Rahal of his his weekend so far. It was pretty comfortable so we were able to push forward and try some things with the set-up and I think we made the race car a lot better.
"It's definitely going to be interesting to follow a bunch of cars based on what some guys were saying that I talked to that seemed to struggle pretty bad so it's going to be an interesting race," suggested Rahal, who took his second career IndyCar win last time out at Fontana.
"I didn't really get a run there at the end of the session to get the most out of the car, but it's definitely pretty good," he added.
With Ganassi's Charlie Kimball in fourth place followed by a brace of Hondas in the form of AJ Foyt Racing's Takuma Sato and Schmidt Peterson Motorsports' James Jakes, the top six ended up being evenly split between the two manufacturers.
Tony Kanaan (Ganassi), defending race winner Will Power (Penske), Sebastien Bourdais (KVSH Racing) and Gabby Chaves (Bryan Herta Autosport) rounded out the top ten, which were covered by just 0.2630s on the one-mile circuit.
The top 16 cars were covered by half a second, and all but one of the 24 cars taking part in the practice session were within one second of Newgarden's time, the sole exception being Pippa Mann in the Dale Coyne Racing #18.
"I definitely knew coming into this weekend that coming here in an IndyCar for the first time was going to be a challenge, and man, this place is really tough," admitted the London-born driver, who turned the most number of laps in the session with 65 revolutions around the Milwaukee Mile.
"We have one more practice session before we go racing and there is definitely a lot of work left for me to do," Mann said. "We have a little to work on with the #18 car and we are just going to keep digging and keep working at it."
Another English driver returning to action this weekend is Justin Wilson, back in the #25 Andretti Autosport for the first time since the Indianapolis 500 at the end of May.
"It's good to be back in the car," said Wilson, who in the meantime had raced for the Andretti team in the Moscow Formula E event. "We just have the one session today to feel everything out, obviously lots to work on.
"We had a slight issue with getting telemetry on the car [on Saturday]," said Wilson, who was 16th fastest yesterday but could only manage 22nd in the Sunday morning session. "It limited the amount of track time we actually got. There [was] lots to think about overnight.
"Practice 2 was going well, I was very happy with the car but our new tyre run at the end was terrible. Qual next, time to sort it," he added later on Twitter. "I'm just pleased to be back."
There was just one brief yellow during practice for a track inspection. Tony Kanaan made the fewest laps for the session with just 30 times around the track.
There is now only a brief interval before the cars return to action for qualifying. That will take the usual form for ovals of single-car time trials posting a two-lap average, rather than the group elimination process used by the series for street and road courses. Qualifying is set to get underway at 12.30pm (6.30pm BST).
The drivers won't get much rest after that, either, before the start of the ABC Supply Co. Inc. Wisconsin 250 at Milwaukee IndyFest itself which will get the green flag shortly after 4.30pm (10.30pm BST). The two-hour race will consist of 250 laps, or 253.75 miles.
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