Bourdais posted a 1m34.732s to head the times 15 minutes from the end of the one-hour session aboard his Chip Ganassi Racing Cadillac Daytona Prototype international.
That eclipsed his 1m34.949s that put the #01 Caddy DPi-V.R at the top of the timesheets early in another session affected by rain.
The track was slightly damp when the green flag was waved and there were further spots of rain mid-session, but times were coming down when the session was red-flagged with just under 10 minutes remaining.
The session yielded the first representative times of the week ahead of a race that will be held in dry but cold conditions according to weather forecasts.
Bourdais's lap compared with the fastest practice lap of 1m34.351s from last weekend's pre-race Roar test and the 1m34.034s that gave JDC-Miller driver Tristan Vautier pole position for the grid-setting 100-mile qualifying race won by Wayne Taylor Racing's Acura ARX-05.
Loic Duval had just gone second in the JDC-Miller Caddy when the interruption came, the Frenchman posting a 1m35.095s.
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Jose Maria Lopez ended up third fastest quickest in the best of the Action Express Racing Cadillacs with a 1m35.235.
Earl Bamber took fourth with a 1m35.587s in the second Ganassi car and reigning IMSA champion Pipo Derani fifth with a 1m35.959s for Action Express as Cadillac blocked out the top five positions.
The two Acuras jumped up the order straight after the session restarted with five minutes left on the clock.
A 1m36.049s from Alex Rossi put the WTR Acrua sixth, while Tom Blomqvist improved to 1m36.347s to end up seventh for Meyer Shank Racing.
The late run from the Acuras demoted Phil Hanson in the fastest of the LMP2s to eighth position overall.
The Briton's 1m37.639s in the United Autosports ORECA-Gibson 07 put him just five hundredths ahead of Ferdinand Habsburg's 1m37.689s in the Tower Motorsport entry.
Harry Tincknell was a further two tenths back in third in class in the PR1 Mathiasen ORECA.
Mirko Bortolotti led the GT Daytona Pro field in his TR3 Racing Lamborghini Huracan GT3 Evo.
The Italian's 1m46.085s put him two tenths up on Matteo Cairoli's 1m46.334s in the Proton-run WeatherTech Racing Porsche 911 GT3 R.
Jack Hawksworth took third in the best of the Vasser Sullivan Lexus R CF GT3s.
The Briton's 1m46.372s was just a couple of hundredths faster than Jan Heylen managed in the Wright Motorsports Porsche to head the GTD pro-am class times.
Andretti Autosport led the way in LMP3, Rasmus Lindh's 1m44.015s in his Ligier-Nissan JSP320 giving him nearly a half-second margin on Kranz Moritz in the fastest of the Muhlner Motorsport Duqueine D08s.
The session was the final time the 61-car field will take to the track ahead of the race, which starts at 1:40pm local time on Saturday.
FP4 Classification:
| Cla | Driver | Class | Chassis | Laps | Time | Gap |
|---|---|---|---|---|---|---|
| 1 |
 Renger van der Zande  Sébastien Bourdais  Scott Dixon  Alex Palou
| DPi | Cadillac DPi | 26 | 1'34.732 | |
| 2 |
Tristan Vautier  Richard Westbrook Loic Duval  Ben Keating
| DPi | Cadillac DPi | 26 | 1'35.095 | 0.363 |
| 3 |
 Mike Rockenfeller  Kamui Kobayashi Jimmie Johnson  Jose Maria Lopez
| DPi | Cadillac DPi | 25 | 1'35.235 | 0.503 |
| 4 |
Earl Bamber Alex Lynn  Marcus Ericsson  Kevin Magnussen
| DPi | Cadillac DPi | 25 | 1'35.587 | 0.855 |
| 5 |
 Pipo Derani Tristan Nunez Mike Conway
| DPi | Cadillac DPi | 27 | 1'35.959 | 1.227 |
| 6 |
Ricky Taylor  Filipe Albuquerque Alexander Rossi Will Stevens
| DPi | Acura DPi | 24 | 1'36.049 | 1.317 |
| 7 |
Oliver Jarvis Tom Blomqvist Helio Castroneves Simon Pagenaud
| DPi | Acura DPi | 14 | 1'36.347 | 1.615 |
| 8 |
Jim McGuire Guy Smith Philip Hanson Will Owen
| LMP2 | ORECA LMP2 07 | 17 | 1'37.639 | 2.907 |
| 9 |
 John Farano  Louis Deletraz Rui Pinto  Ferdinand Habsburg
| LMP2 | ORECA LMP2 07 | 22 | 1'37.689 | 2.957 |
| 10 |
Thomas Steven Josh Pierson Jonathan Bomarito Harry Tincknell
| LMP2 | ORECA LMP2 07 | 21 | 1'37.864 | 3.132 |
| 11 |
Ben Keating Mikkel Jensen Scott Huffaker Nicolas Lapierre
| LMP2 | ORECA LMP2 07 | 22 | 1'37.938 | 3.206 |
| 12 |
Frits van Eerd Giedo van der Garde Murry Dylan Rinus van Kalmthout
| LMP2 | ORECA LMP2 07 | 22 | 1'38.186 | 3.454 |
| 13 |
John Falb  James Allen  Luca Ghiotto Tijmen van | LMP2 | ORECA LMP2 07 | 26 | 1'38.214 | 3.482 |
| 14 |
Eric Lux Devlin DeFrancesco  Patricio O'Ward Colton Herta
| LMP2 | ORECA LMP2 07 | 26 | 1'38.286 | 3.554 |
| 15 |
Dwight Merriman Kyle Tilley Ryan Dalziel Paul-Loup Chatin
| LMP2 | ORECA LMP2 07 | 7 | 1'38.362 | 3.630 |
| 16 |
Dennis Andersen Anders Fjordbach Fabio Scherer Nico Mueller | LMP2 | ORECA LMP2 07 | 14 | 1'39.046 | 4.314 |
| 17 |
François Heriau Oliver Rasmussen  Ed Jones René Rast
| LMP2 | ORECA LMP2 07 | 23 | 1'39.359 | 4.627 |
| 18 |
Jarett Andretti Josh Burdon Rasmus Lindh  Gabby Chaves
| LMP3 | Ligier JS P320 | 21 | 1'43.594 | 8.862 |
| 19 |
Efrin Castro Moritz Kranz Ori Ayrton Joel Miller
| LMP3 | Duqueine D08 | 17 | 1'44.384 | 9.652 |
| 20 |
Nolan Siegel Cameron Shields Charles Crews Ugo De | LMP3 | Duqueine D08 | 24 | 1'44.465 | 9.733 |
| 21 |
Mark Kvamme Austin McCusker Trenton Estep Antoine Doquin | LMP3 | Duqueine D08 | 15 | 1'44.605 | 9.873 |
| 22 |
Joao Barbosa Malthe Jakobsen Seb Priaulx Lance Willsey
| LMP3 | Ligier JS P320 | 17 | 1'44.879 | 10.147 |
| 23 |
Orey Fidani Kuno Wittmer Lars Kern Matthew Bell
| LMP3 | Duqueine D08 | 23 | 1'45.229 | 10.497 |
| 24 |
Marco Mapelli Andrea Caldarelli Mirko Bortolotti Rolf Ineichen
| GTD PRO | Lamborghini Huracan GT3 | 14 | 1'46.085 | 11.353 |
| 25 |
Cooper MacNeil Julien Andlauer Matteo Cairoli  Alessio Picariello
| GTD PRO | Porsche 911 GT3 R | 24 | 1'46.334 | 11.602 |
| 26 |
Jack Hawksworth Ben Barnicoat Kyle Kirkwood
| GTD PRO | Lexus RC F GT3 | 24 | 1'46.372 | 11.640 |
| 27 |
Ryan Hardwick Zacharie Robichon Jan Heylen Richard Lietz
| GTD | Porsche 911 GT3 R | 23 | 1'46.399 | 11.667 |
| 28 |
Cooper MacNeil Daniel Juncadella Maro Engel Jules Gounon
| GTD PRO | Mercedes-AMG GT3 | 20 | 1'46.534 | 11.802 |
| 29 |
Dirk Muller Patrick Assenheimer Austin Cindric
| GTD PRO | Mercedes-AMG GT3 | 15 | 1'46.595 | 11.863 |
| 30 |
Matt Campbell Mathieu Jaminet Felipe Nasr
| GTD PRO | Porsche 911 GT3 R | 24 | 1'46.622 | 11.890 |
| 31 |
Kenny Habul Luca Stolz Raffaele Marciello Fabian Schiller
| GTD | Mercedes-AMG GT3 | 28 | 1'46.685 | 11.953 |
| 32 |
Laurens Vanthoor Patrick Pilet  Dennis Olsen Alexandre Imperatori
| GTD PRO | Porsche 911 GT3 R | 21 | 1'46.730 | 11.998 |
| 33 |
Michael de Quesada Daniel Morad Linus Lundqvist Maximillian Goetz | GTD | Mercedes-AMG GT3 | 23 | 1'46.856 | 12.124 |
| 34 |
Mike Skeen Guy Cosmo Stevan McAleer Scott Andrews
| GTD | Mercedes-AMG GT3 | 17 | 1'46.930 | 12.198 |
| 35 |
Kyffin Simpson Till Bechtolsheimer Marc Miller Mario Farnbacher
| GTD | Acura NSX GT3 | 21 | 1'46.936 | 12.204 |
| 36 |
Franck Perera LLarena Mateo Paul Maximilian Mikhail Goikhberg
| GTD | Lamborghini Huracan GT3 | 24 | 1'46.942 | 12.210 |
| 37 |
Ted Giovanis Hugh Plumb Matt Plumb Owen Trinkler
| GTD | Porsche 911 GT3 R | 14 | 1'47.037 | 12.305 |
| 38 |
Alessandro Pier Guidi James Calado Daniel Serra Davide Rigon
| GTD PRO | Ferrari 488 GT3 | 25 | 1'47.120 | 12.388 |
| 39 |
Dan Goldburg Hikaru Abe Garett Grist Nicolas Pino | LMP3 | Ligier JS P320 | 16 | 1'47.125 | 12.393 |
| 40 |
Tommy Milner Nick Tandy Marco Sorensen
| GTD PRO | Corvette C8.R GTD | 26 | 1'47.167 | 12.435 |
| 41 |
Rob Ferriol Katherine Legge Stefan Wilson Nicholas Boulle
| GTD | Porsche 911 GT3 R | 23 | 1'47.199 | 12.467 |
| 42 |
Kyle Washington James Sofronas Jeroen Bleekemolen Klaus Bachler
| GTD | Porsche 911 GT3 R | 22 | 1'47.204 | 12.472 |
| 43 |
Frankie Montecalvo Aaron Telitz Richard Heistand Townsend Bell
| GTD | Lexus RC F GT3 | 23 | 1'47.269 | 12.537 |
| 44 |
Ross Gunn Alex Riberas Maxime Martin
| GTD PRO | Aston Martin Vantage GT3 | 17 | 1'47.294 | 12.562 |
| 45 |
Robby Foley Bill Auberlen Michael Dinan Jens Klingmann
| GTD | BMW M4 GT3 | 22 | 1'47.360 | 12.628 |
| 46 |
Connor de Phillippi John Edwards Augusto Farfus  Jesse Krohn
| GTD PRO | BMW M4 GT3 | 23 | 1'47.363 | 12.631 |
| 47 |
Roman De Angelis Ian James Darren Turner Tom Gamble | GTD | Aston Martin Vantage GT3 | 22 | 1'47.371 | 12.639 |
| 48 |
Russell Ward Philip Ellis Mikael Grenier Lucas Auer
| GTD | Mercedes-AMG GT3 | 23 | 1'47.416 | 12.684 |
| 49 |
Brendan Iribe Frederik Schandorff Ollie Millroy  Jordan Lee Pepper
| GTD | McLaren 720S GT3 | 21 | 1'47.443 | 12.711 |
| 50 |
Roberto Lacorte Giorgio Sernagiotto Antonio Fuoco Alessio Rovera
| GTD | Ferrari 488 GT3 | 27 | 1'47.559 | 12.827 |
| 51 |
Lance Bergstein Jon Miller Patrick Gallagher Paul Holton
| GTD | McLaren 720S GT3 | 17 | 1'47.569 | 12.837 |
| 52 |
Paul Dalla Lana David Pittard Charlie Eastwood Nicki Thiim
| GTD | Aston Martin Vantage GT3 | 15 | 1'47.780 | 13.048 |
| 53 |
John Potter Andy Lally Spencer Pumpelly Jonathan Adam
| GTD | Aston Martin Vantage GT3 | 26 | 1'47.878 | 13.146 |
| 54 |
Antonio Garcia Jordan Taylor Nick Catsburg
| GTD PRO | Corvette C8.R GTD | 21 | 1'47.924 | 13.192 |
| 55 |
Robert Megennis Corey Lewis Sandy Mitchell Jeff Westphal
| GTD | Lamborghini Huracan GT3 | 19 | 1'48.580 | 13.848 |
| 56 |
Mann Simon Luis Perez Companc Nicklas Nielsen Toni Vilander
| GTD | Ferrari 488 GT3 | 26 | 1'48.766 | 14.034 |
| 57 |
Philipp Eng Marco Wittmann Nick Yelloly Sheldon Van Der Linde
| GTD PRO | BMW M4 GT3 | 17 | 1'48.873 | 14.141 |
| 58 |
Don Yount Benja Hites Jaden Conwright Markus Palttala
| GTD | Lamborghini Huracan GT3 | 21 | 1'49.166 | 14.434 |
| 59 |
Bill Sweedler John Megrue Giacomo Altoè Jeff Segal
| GTD | Lamborghini Huracan GT3 | 13 | 1'49.191 | 14.459 |
| 60 |
Jon Bennett Colin Braun George Kurtz Nic Jönsson
| LMP3 | Ligier JS P320 | 0 | 0.000 | |
| 61 |
Gar Robinson Felipe Fraga Kay van Berlo Michael Cooper
| LMP3 | Ligier JS P320 | 5 | 0.000 | |
| View full results | ||||||
