Max Verstappen and Daniel Ricciardo proved Red Bull will be tough to beat this weekend as they led a comfortable one-two in first practice for the Mexican Grand Prix.
It was the Dutchman who held a four-tenth advantage over his Australian teammate as he got a clear lap when his Hypersoft tyres were still new, whereas Ricciardo had to wait until the second timed lap to set his best time.
The reason for Red Bull's strength is the thinner air at higher altitude in Mexico City which negates Renault's engine deficit compared to Mercedes and Ferrari.
In fact, it was the French manufacturer who had their cars in third and fourth as Carlos Sainz and Nico Hulkenberg also opted to run the pink-striped compound throughout the first 90 minutes.
On the weekend when Lewis Hamilton is expected to secure his fifth world title, the Briton was fifth fastest in his Mercedes ahead of Valtteri Bottas, this despite complaining about dips in power during his second run.
Both Mercedes and Ferrari also switched to the Ultrasoft tyre after the first 40-minute change with Sebastian Vettel and Kimi Raikkonen following the Silver Arrows in seventh and eighth.
A key focus for the Scuderia was on a new floor which Red Bull has also copied as they look to work out why a rollback of upgrades has seemingly unlocked the pace that had gone missing in recent races.
On the very dusty Autodromo Hermanos Rodriguez circuit, braking was also a problem for Ferrari as Vettel and Raikkonen suffering big lock-ups into Turn 1 with Kimi also spinning at Turn 6.
Another thing the lack of grip was doing was ruining the Hypersoft tyre with graining a big problem very quickly and likely causing the decision for many teams to switch to the more durable Ultrasoft.
Brendon Hartley even described his tyres as little bubblegum at one point as the Kiwi finished P9 in the Toro Rosso and Nicholas Latifi when faster than Force India regular Sergio Perez in 10th.
The big home favourite was only 0.046s back in 11th and set his best on the slower Ultra compared to the Canadian F2 driver on the Hypersoft.
Antonio Giovinazzi also beat Marcus Ericsson, the man he'll be replacing at Sauber for next season in P12 with the Swede three-tenths back in P14 on the same tyre.
Romain Grosjean was 14th in the first of the Haas' with Lando Norris ahead of Stoffel Vandoorne in 15th and 16th respectively for McLaren.
The two Williams' brought up the field with Pierre Gasly only completing an installation lap before returning to the garage as Toro Rosso change his engine, something that will result in more grid penalties for the Frenchman.
Full results from Practice 1 can be seen below:
Whiting: Ocon 'wrong' to fight Verstappe
Raikkonen believes P3 the best he could
Ricciardo: 'Every time we start out of p
McLaren 'confident' Indy 500 plans won't
Red Bull call for Ocon race ban as Verst
Mercedes reveal Hamilton had 'failure im
Vettel gives Brazil race 'one out of ten
Hamilton tells Verstappen: 'You had more
Hamilton 'proud' of Mercedes as double c
Ocon claims Verstappen 'wanted to punch
Brazil GP: Hamilton inherits victory as
Ricciardo jokes 0.002s loss to Max 'more
Alonso & McLaren confirm Indy 500 return
Hamilton blasts 'disrespectful' Sirotkin
Vettel slams FIA weighbridge process aft
Brazil GP: Hamilton beats Vettel to pole
Brazil GP: Vettel sets new lap record in
Ferrari's Clear to have key Leclerc role
Hamilton says 25-race calendar would dri
'Realistic' Verstappen insists Red Bull
Red Bull reveal a Mexico marshal caused
Vettel expects Ferrari progress in Brazi
Williams offer Kubica 2019 seat but Ferr
Red Bull see race potential even if Braz
Brazil GP: Bottas pips Hamilton by 0.003
Brazil GP: Verstappen leads Vettel & Ham
Tyres and two-tier F1 to dominate driver
Verstappen: Mexico anger post-qualifying
Hamilton doubts Bottas would want F1 win
Alonso: McLaren optimistic 2019 car will
Ocon rejecting non-F1 offers to 'stay cl
Massa: Vettel 'more guilty' for 2018 tit
Hamilton to Leclerc & Gasly: 'No substit
Red Bull: 2019 front wings a costly 'sho
Sainz claims Schumacher name alone won't
Bottas: Hamilton's adaptability is his b
Force India: Signs point to Stroll being
Liberty want to 'preserve' classic F1 ra
Williams still getting over 'enormous sh
Hamilton doubts he would have recovered
Brazil step up security ahead of F1 race
Vietnam confirmed for 2020 F1 calendar
Studious Schumacher 'not as crazy' as Ve
Arrivabene: Ferrari still lack winning '
Ferrari CEO admits F1 budget cap 'makes
Mercedes target tyre woes and Constructo
Force India see catching F1's big three
Sainz has no issue with Renault over sig
Ferrari slam 'fake' Binotto rumours aime
Smedley confirms Williams departure afte
Sauber: Don't compare Leclerc to Hamilto
Two prospective manufacturers rule out F
Magnussen claims current cars leave F1 d
Red Bull: Immediate Gasly comparisons to
Vettel: 2018 Ferrari 'strong' but never
Webber fears Renault a threat to Ricciar
Hamilton: Bottas relationship as teammat
Magnussen: Haas should be 'proud' to be
Tombazis: FIA had to 'intervene' with 20
Zandvoort reportedly offered 2020 Dutch
Vettel wants himself & Leclerc to 'work
Mercedes: 'This is the best Lewis Hamilt
Ricciardo confirms participation in fina
Haas fail in bid to overturn Grosjean's
F1 bosses warn of 'step backwards' with
Hamilton believes Alonso made one crucia
Verstappen 'absolutely' ready as Red Bul
Hamilton: Monza victory a 'psychological
Horner: 'Only Daniel' Ricciardo knows of
Vettel 'past his peak' and lacks Ferrari
Mercedes praise Ferrari for 'gloves-off'
Hartley informed of Toro Rosso exit afte
Kubica to fill development role at Ferra
Verstappen's go after Ricciardo & Hamilt
Horner gives Renault rare credit after M
Hamilton could never consider himself Fo
Gasly questions Ocon's racing style afte
Mexico retirement 'hurts a lot' for Pere
Ericsson left 'fuming' after 'sacrificin
Vandoorne frustrated only points-scoring
Hamilton credits 'special moments' as ke
Bottas targets victory in Brazil & Abu D
Ecclestone: Formula 1 needs Hamilton 'mo
Vettel: Hockenheim crash not decisive in
Ricciardo doesn't 'see the point' in rac
Verstappen hails start for 'amazing' Mex
Mercedes boss Wolff had to compose himse
Vettel concedes Hamilton 'better' after
Hamilton 'humbled' by fifth Formula 1 ti
Mexico GP: Verstappen victorious as Hami
Hamilton wary of the 'red car behind' at
Vettel suggests Red Bull could 'beat the
Ricciardo elated, Verstappen deflated af
Mexico GP: Ricciardo beats Verstappen to
Mexico GP: Verstappen leads, Bottas hits
Vettel expecting 'big jumps' as teams un
Sainz doesn't see P3 as representative o
Hamilton uncertain of challenging Red Bu
Verstappen plays down practice stoppage
Bottas feels he could still be fighting