Red Bull's Sergio Perez lapped fastest in final practice for his home Mexico City Grand Prix on Saturday with Formula One championship-leading team mate Max Verstappen second and Mercedes far behind.
The 31-year-old home hero, who has never stood on the podium in Mexico, posted a best effort of 1:17.024 seconds at the high altitude Autodromo Hermanos Rodriguez with Verstappen 0.193 slower.
The crowd gave a huge roar at Perez's time which his team mate, struggling for grip, did not try and beat in the dying seconds.
Seven times world champion Lewis Hamilton, 12 points adrift of Verstappen in the championship with five races remaining, was third fastest for Mercedes but 0.651 off Perez's pace. Team mate Valtteri Bottas was fourth.
"Six and a half tenths?," said a disbelieving Hamilton over the radio after being told of the gap.
Carlos Sainz was fifth fastest for Ferrari, whose chances of overtaking McLaren for third place overall were boosted by Lando Norris taking a new engine that sends him to the back of the field for exceeding his season's allowance.
The Briton can still provide a useful aerodynamic tow for Australian team mate Daniel Ricciardo in Saturday's later qualifying.
Alpine's Esteban Ocon, AlphaTauri's Yuki Tsunoda and Aston Martin's Lance Stroll also have similar penalties while Williams' George Russell drops five for replacing his car's gearbox.
An oil spill from earlier support races made the track slippery in the stadium sector, with cement dust laid down over it and drivers waiting for it to settle before starting the session.
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