Ed Carpenter still managed to crack the 230mph barrier despite rain and hail limiting running to less than 20 minutes on 'Fast Friday', the final Indianapolis 500 practice before qualifying.
Carpenter, who won pole for last year's race, achieved a best average speed of 230.522mph on a day when the top seven drivers all went above 229mph.
Three-time winner Helio Castroneves was second-fastest at 220.843mph, with Marco Andretti, JR Hildebrand and Josef Newgarden rounding out the top five.
"When it comes to predicting what the pole [speed] is going to be, I think a lot of it will be figuring out what the weather is," said Carpenter.
"If it warms up enough and the air gets a little thinner, certainly I think 230s are realistic, even up to 232 and 233."
The day marked the first time that IndyCar teams could work with the higher qualifying boost levels, which are turned up from 130 kPa to 140 kPa from Friday through the two days of qualifying on Saturday and Sunday.
The engines, which deliver an estimated additional 40bhp in that spec, will then be returned to their previous boost levels for Carb Day and the race.
Jacques Villeneuve, who won the 1995 Indy 500, admitted that the poor weather had left him feeling ill-prepared for qualifying, but said that his priority is to have a car that works in the race.
"We have no idea what to expect for tomorrow," said the Canadian, who ended the day 16th-fastest.
"We were on old tyres in the few laps we got on Fast Friday and we hadn't trimmed the car out yet. I also had a little bit of a tow on those laps. We haven't even done a practice qualification run yet.
"We're not under any stress though, because we're not in the points championship. Qualifying is almost meaningless for us, so there's no point in us taking a risk with anything. What matters for us is the race."
Under the new Indy 500 qualifying system, Saturday's session will formally decide the 33 cars that will make up the grid.
On Sunday, the cars will return to the track to determine the starting order for next weekend's race.
Pos Driver Team/Engine Speed Time Gap Laps
1. Ed Carpenter Carpenter/Chevy 230.522 39.0418s 8
2. Helio Castroneves Penske/Chevy 229.843 39.1571s +0.1153s 9
3. Marco Andretti Andretti/Honda 229.419 39.2296s +0.1878s 4
4. JR Hildebrand Carpenter/Chevy 229.384 39.2355s +0.1937s 8
5. Josef Newgarden Fisher/Honda 229.276 39.2540s +0.2122s 6
6. Juan Pablo Montoya Penske/Chevy 229.205 39.2662s +0.2244s 7
7. Scott Dixon Ganassi/Chevy 229.062 39.2907s +0.2489s 11
8. Ryan Hunter-Reay Andretti/Honda 228.603 39.3695s +0.3277s 7
9. Simon Pagenaud Schmidt/Honda 228.544 39.3798s +0.3380s 8
10. Jack Hawksworth Herta/Honda 228.176 39.4432s +0.4014s 6
11. James Hinchcliffe Andretti/Honda 228.115 39.4537s +0.4119s 8
12. Martin Plowman Foyt/Honda 228.036 39.4675s +0.4257s 7
13. Carlos Munoz Andretti/Honda 227.938 39.4844s +0.4426s 11
14. Mikhail Aleshin Schmidt/Honda 227.822 39.5046s +0.4628s 8
15. Takuma Sato Foyt/Honda 227.741 39.5186s +0.4768s 5
16. Jacques Villeneuve Schmidt/Honda 227.682 39.5288s +0.4870s 6
17. Alex Tagliani Fisher/Honda 227.394 39.5788s +0.5370s 4
18. Oriol Servia Rahal/Honda 226.387 39.7550s +0.7132s 8
19. Sebastien Bourdais KV/Chevy 226.351 39.7612s +0.7194s 7
20. Sebastian Saavedra KV/Chevy 226.137 39.7988s +0.7570s 5
21. Ryan Briscoe Ganassi/Chevy 226.072 39.8103s +0.7685s 5
22. Will Power Penske/Chevy 223.202 40.3222s +1.2804s 7
23. Kurt Busch Andretti/Honda 217.145 41.4470s +2.4052s 8
24. Charlie Kimball Ganassi/Chevy 2
25. Graham Rahal Rahal/Honda 2
26. Carlos Huertas Coyne/Honda 1
All drivers use Dallara chassis