Ahead of today's opening session the air temperature is 22 degrees C, while the track temperature is 36 degrees.
With just four races remaining, it's time for the teams to start giving serious consideration to the rule whereby they have to run a rookie in at least two sessions over the course of the season, hence we have no less than five on duty this morning.
They being: Frederik Vesti replacing George Russell at Mercedes, Oliver Bearman replacing Magnussen at Haas, Theo Pourchaire replacing Valtteri Bottas at Alfa Romeo, Jack Doohan replacing Pierre Gasly at Alpine and Isack Hadjar replacing Yuki Tsunoda at AlphaTauri.
In terms of upgrades, Red Bull has new Cooling Louvres as does Ferrari and Alpine, which also has a new Engine Cover.
McLaren has a new Engine Cover and Front Corner, while Alfa Romeo has a new Rear Corner and Haas a new Front Corner Circuit and Cooling Louvres.
AlphaTauri brings a new Front Corner and Engine Cover, while Williams has a new Engine Cover and Cooling Louvres.
Due to the unique nature of this track almost all of these are circuit specific.
Compounds this weekend are the C%, C4 and C3 a step softer than last year. Furthermore, today Pirelli is trying out a new variant of the C4, with each driver given two sets of the prototypes to use as they wish. Pirelli will subsequently analyse the data before deciding whether or not to homologate the compound for use in 2024.
The lights go green and Alonso leads the way, followed by Stroll, Piastri, Zhou and Albon. While the McLaren driver is on mediums, the majority are on hards, though a few are on the prototypes.
Among the first to head out, much to the delight of the partisan crowd, is Perez.
Of the first wave Perez goes quickest, crossing the line at 23.935. Albon goes second, ahead of Sainz, Leclerc and Verstappen.
"I've got an engine problem, no power," reports Stroll. However, he is told there is not an issue.
A 23.853 sees Piastri go quickest.
Tsunoda, having taken on a new engine, looks set to take a grid drop on Sunday.
On a day there are three Australians in action, Ricciardo goes quickest with a 23.555. However, Albon responds with a 22.466.
"The engine makes a slight strange noise when I'm on full throttle," reports Leclerc.
"There's something metal on the pit straight," reports Piastri, the something appearing to have come off Ricciardo's car.
No sooner has Albon consolidated his top spot with a 22.419 than Verstappen responds with a 21.858.
"I lost the car... hydraulics," reports Sainz, "I will try and make it back but no power steering." He subsequently pits.
The crowd roars as Perez goes top with a 21.596.
"Something's happened... it's like the throttle's stuck, it over-revs like hell," reports Norris. The Briton is one of three drivers yet to post a time, Pourchaire and Doohan being the others.
Verstappen - like his teammate on the mediums - goes quickest with a 20.425.
The majority of the field are now running the prototypes.
Norris encounters a slow Doohan causing the McLaren driver to go wide at Turn 12.
There is clearly something wrong at Ferrari where mechanics are swarming over the rear of Sainz's car which is up on its stand. Leclerc, currently fourth, is also in the pits.
Albon (mediums) splits the Bulls with a 20.249, just 0.004s down on Verstappen.
With 38 minutes remaining, Piastri is the first to switch to the softs, the Australian subsequently posting a 20.844 to go fourth.
A big slide for Doohan as Albon bolts on the prototypes.
Leclerc, currently 7th, heads out on softs as Hamilton (proto) improves to ninth.
Ricciardo (mediums) goes fourth with a 20.694.
On the softs Leclerc improves to third with a 20.297 as Sargeant goes seventh, ahead of Zhou, Norris and Hulkenberg.
With 28 minutes remaining, Bearman (12th) is currently the quickest rookie, ahead of Hadjar, Doohan, Vesti and Pourchaire, who, like Alonso, has yet to post a time.
The Bulls switch to the softs, as do Norris, Vesti, Ocon and Zhou.
On those red-banded tyres Norris goes quickest (20.237), but he is subsequently leapfrogged by Verstappen (19.718), while Perez, after going quickest in S1, runs into traffic in S2.
Hadjar, left-hand side of his car smothered in flo-vis, runs wide.
"I need to box, there is something between my feet which is loose," reports Verstappen.
Norris (softs) goes second with a 20.237 as Stroll goes seventh, ahead of Ricciardo and Hamilton.
Alonso finally set a time, the two-time champ going 17th with a 22.900 on the prototypes.
Perez improves to second just 0.095s off his teammate's pace.
Pourchaire's session appears to be at an end, the Frenchman is out of his car after just 4 laps.
Albon displaces Perez with a 19.813, the Williams driver looking remarkably strong here today.
With just under 10 minutes remaining, Sainz is back on track.
Hadjar goes quickest of the rookies, the French-Algerian posting a 21.941 to go 15th.
A scrappy lap from Bearman who appears to be pushing too hard.
Perez runs wide in Turn 4 as he appears to battle Norris for position.
Alonso improves to 14th (21.347) on the hards, the Spaniard seemingly running with the upgrades introduced - and then rejected by him - in Austin.
Hulkenberg improves to 12th with a 20.968 just moments before the session ends, as Bearman leapfrogs Alonso.
He's third, but Perez gets a huge roar from the crowd as the session ends.
Verstappen is quickest, ahead of Albon, Perez, Norris, Leclerc, Piastri, Sainz, Ricciardo, Ocon and Stroll.
Hamilton is eleventh, ahead of Hulkenberg, Zhou, Sargeant, Bearman, Alonso, Hadjar, Doohan, Vesti and Pourchaire.
Check out our Friday gallery from Mexico City here.
sign in