Daniel Ricciardo set a new track record to guarantee top spot in an incredibly tight second practice session on Friday afternoon in Mexico, in which just 0.163s split the top three - and less than half a second covered the top six.
Championship leader Lewis Hamilton finished barely a tenth down the road in second, but he had Max Verstappen in the second Red Bull for close company - the Dutchman in fact just three hundredths of a second slower than the lead Mercedes.
Ferrari then followed up in fourth and fifth - Sebastian Vettel fractionally ahead of team mate Kimi Raikkonen - with FP1 pacesetter Valtteri Bottas ending the session in sixth, half a second down on his team mate.
McLaren's Fernando Alonso continued his strong form to claim seventh, ahead of a tight battle between the Force Indias and Renaults - one that was eventually settled in home favourite Sergio Perez's favour, with Nico Hulkenberg, Esteban Ocon and Carlos Sainz all fractions of a second down the road.
The session itself was littered with errors and issues - most notably for Romain Grosjean, whose tyre delaminated just after a spin, with the spewed carcass and bodywork damage triggering red flags for a clean-up. Grosjean completed just three laps as a result, well down on the leading tally of 43, set by Bottas.
Several other drivers - including Hamilton, Toro Rosso's Brendon Hartley and Williams' Lance Stroll - had spins, although all escaped relatively unscathed.
Verstappen meanwhile was amongst those to encounter technical gremlins - an engine issue forcing the Dutchman to bring his session to a slightly early halt. Toro Rosso's Pierre Gasly, back in for FP1 stand-in Sean Gelael, also hit issues and completed just 10 laps, leaving him 19th - just ahead of Grosjean.