Andre Lotterer set the pace in the opening practice session as Porsche showed strong pace in Mexico City.
The German driver set a time of 1:07.509 and spent most of the session heading a Porsche 1-2 ahead of Pascal Wehrlein.
Only Sebastien Buemi’s late flyer in the Nissan was able to split the Porsche drivers.
Behind them, Robin Frijns was fourth quickest for Envision Racing, ahead of DS Techeetah’s Antonio Felix da Costa, who was one of a handful of drivers to take to the escape road at Turn 1.
Lucas di Grassi, Sergio Sette Camara, and on two occasions, Alexander Sims were the others to make an excursion there.
Maximillian Guenther was sixth in the other Nissan ahead of Mercedes’s Nyck de Vries.
Nick Cassidy was eighth fastest for Envision, with the top 10 being completed by Andretti’s Jake Dennis and Jean-Eric Vergne in the DS Techeetah.