Race leader Ricky Taylor brought the 55th Rolex 24 at Daytona into its final quarter with the #10 Cadillac DPi-V.R. holding a 12 second advantage over João Barbosa.
Taylor, driving the car entered by Wayne Taylor Racing, headed up the overall order following a rain-affected early morning segment at Daytona International Speedway.
Rolex 24 Results after 18 Hours
Hours 12 to 18 were marked by a lengthy caution period lasting almost two hours as drivers struggled to contend with a downpour during the night.
Only three cars remain on the lead lap, with the #5 Action Express Racing DPi-V.R. and the Visit Florida Racing Riley Mk.30 set to challenge the Taylor car for the win.
The Visit Florida squad moved into the lead of the race in the 13th hour when Taylor's team-mate Max Angelelli was called to serve a drive through penalty for a pit stop violation.
IMSA officials deemed the Wayne Taylor Racing mechanics to have inserted the fuel flow pump too early during a routine service.
Visit Florida driver Rene Rast continued to hold stead at the sharp end of the field before handing the Riley over to Marc Goossens during the extended caution period.
Goossens then dropped to third at the restart, with Filipe Albuquerque (#5 Cadillac) and Taylor managing to slip past.
In the 17th hour Taylor took the lead with a late-braking manoeuvre on Albuquerque heading into the chicane.
In GTLM, Porsche and Ford continued their scrap for the class lead with the sole remaining Corvette completing the top three.
At the close of the 18th hour it was the #911 Porsche 911 RSR of Patrick Pilet in front, with Sebastien Bourdais running just 4.5 seconds behind in the pole-sitting #66 Ford GT.
Jan Magnussen (#3 Corvette), Laurens Vanthoor (#912 Porsche) and Giancarlo Fisichella (#62 Ferrari) are the three other drivers keeping touch with Pilet's lead lap.
The two GT Daytona-class Acura NSX GT3s maintained their reliable debut run at the Rolex 24 with the Michael Shank-entered machines running first and second in category.
IndyCar drivers Ryan Hunter-Reay and Graham Rahal guided the team into the final six hours, ahead of Matt Bell in the Stevenson Motorsports Audi R8.
Prototype Challenge continues to be led by Performance Tech Motorsports.
The turn of the hour concluded with the 14th caution of the event, after a PC car dropped debris in the horseshoe section.