The #5 Cadillac DPi-V.R shared by Westbrook, Tristan Vautier and Loic Duval finished a close second at the Florida airfield track, losing out to the Chip Ganassi Racing Cadillac of Earl Bamber, Alex Lynn and Neel Jani by just over six seconds.
Westbrook took advantage of a drive-through penalty for Bamber in the #02 Ganassi car late in the penultimate hour to move into the lead, but the New Zealander appeared to have a pace advantage and soon repassed.
