Eng, whose BMW is run by Rahal Letterman Lanigan Racing, beat Sebastien Bourdais (Cadillac V-Sequence.R) and the second BMW of Connor De Phillippi within the 90-minute observe session.
This weekend’s 2h40m occasion is being run for GTP and GTD equipment solely.
After the Porsche Penske Motorsport 963s of Nick Tandy and Felipe Nasr swapped the highest spot between them early on, Connor De Phillippi took over within the #25 BMW M Hybrid V8, lapping in 1m14.916s contained in the opening 20 minutes.
Eng then made it a BMW 1-2 in his #24 sister automobile, lapping in a session-topping 1m13.349s as De Phillippi improved to 1m13.722s simply earlier than the midway level.
Bourdais broke up their celebration within the #01 Chip Ganassi Racing-run Cadillac, taking the second spot with 1m13.573s, 0.224s off the quickest time.
Ricky Taylor suffered an early off at Flip 3 within the #10 Wayne Taylor Racing with Andretti Acura ARX-06, the automobile that set the tempo on Friday, and in addition suffered a flat tire later. His off-track second was mirrored by Renger van der Zande within the #01 Cadillac within the second half of the session.
The session was purple flagged with quarter-hour to go when Jarrett Andretti went off at Flip 5 within the Andretti Motorsports Porsche 911 GTD entry.
On the resumption, Eng remained on prime, forward of Bourdais and De Phillippi. Dane Cameron made a late enchancment to take fourth within the #7 factory-run Porsche 963, forward of the sister automobile of Mathieu Jaminet.
Pipo Derani was sixth within the Motion Specific-run Cadillac that Jack Aitken crashed yesterday. Ricky Taylor was seventh, forward of the sister Acura of Louis Deletraz, who improved late on.
Richard Westbrook (JDC-Miller) and Gianmaria Bruni (Proton) rounded out the GTP class of their buyer Porsche 963s.
#14 VasserSullivan Lexus RC F GT3: Jack Hawksworth, Ben Barnicoat
Photograph by: Jake Galstad / Motorsport Images
Lexus beats Corvette in GTD
In GTD, Jack Hawksworth set the tempo in Vasser Sullivan’s #14 Professional class Lexus RC F with 1m20.376s, forward of Nicky Catsburg in his #4 Chevrolet Corvette Z06 GT3.R.
That’s the best way it stayed till the top. Marvin Kirchhofer (Pfaff Motorsports McLaren 720S) was third, simply pipping the highest pro-am entry, the Wayne Taylor Racing with Andretti Lamborghini Huracan of Danny Formal.
Qualifying begins later at 7:35pm ET.