Ahead of today's second session the air temperature is 23.4 degrees C, while the track temperature is a toasty 44 degrees.

While this morning's session was dominated by Red Bull, with Max Verstappen edging out teammate Daniel Ricciardo by 0.483s, it was interesting see the two works Renaults finish third and fourth.

Admittedly, Mercedes and Ferrari were both focussing on updates to their cars, but nonetheless it gives the French manufacturer an early boost.

The bid topic earlier - other than Pierre Gasly starting from the back of the grid again - was grip, or rather lack of it, the drivers really struggling to stay on the black stuff.

Romain Grosjean described running on his hypers like being on wets while Brendon Hartley compared his to bubble gum.

Other than grip, the other issue, as in Austin, was traffic, with Sergey Sirotkin making himself none too popular with a number of rivals.

Despite the lack of grip, there were very few incidents of note other than Sainz taking a trip through the grass, Raikkonen spinning and Lando Norris doing very well to avoid Latifi, who finished the session tenth quickest.

Though concentrating on updates, which suggest the old floor is better than the new one, Ferrari had a tough time of it earlier, appearing to struggle on both the ultras and hypers, with both drivers flat-spotting a couple of pair of each.

Having only completed two laps earlier, Gasly is first out this afternoon, running a brand new old-spec engine. If that makes sense. The Frenchman reports that his steering is pulling to the right.

The Toro Rosso drivers heads back to the pits, at which point Raikkonen heads out, the Finn now trying the supersofts for the first time.

Raikkonen posts the first time of the afternoon, the Ferrari still clearly struggling, it's a 20.027 as the SF71H slides all over the place.

Vettel, like his teammate, out on track surprisingly early, can only manage 20.071, as Leclerc, also on supers, posts 21.990. Ericsson, on ultras, posts 26.484.

Raikkonen improves to 19.761 as the super slo-mo picks up the warping of his rear tyres.

No sooner has Magnussen gone third (21.830), than he is demoted by his teammate (20.567), and then Alonso.

A 19.472 sees Vettel take the top spot as the Silvers Arrows head out, both, like Ferrari, on the supers.

Having gone quickest in S2, Hamilton finally crosses the line at 19.207. Moments later Hulkenberg posts 19.176 and Bottas 19.361.

Vettel improves with a 19.007 as Sainz goes fifth (19.542), ahead of Raikkonen and Grosjean.

It's that man again, from out of nowhere, Albeit on hypers, Hartley produces an 18.928 to go quickest. His teammate, also on the pink-banded rubber, can only manage ninth (19.632). That said, the kiwi has the updated front wing and floor this weekend, while Gasly is running the old versions.

An 18.859 sees Hamilton take his rightful place at the top of the timesheets, but in no time at all he is displaced by Perez and then Verstappen (14.437). The Mexican is on the hypers and the Dutchman on ultras.

Ocon goes fifth, ahead of Vettel, with an 18.943.

A lock up for Hamilton is followed by a bumpy ride over the grass at T1.

"What we're seeing here is that it might be a challenge to get through to Q3 on just the ultrasoft tyre tomorrow," admits Pirelli. "The hypersoft has a notable speed advantage, but of course doesn't last as long."

Though he's late to the party, Ricciardo goes second with a 17.964 on the ultras.

On the evidence thus far, the delta between the ultras and supers is around 1.3s.

For a short while silence descends as all the drivers head back to their garages, but then Vettel emerges having ditched the supers in favour of hypers. He is followed by his teammate who is also on the pink-banded rubber.

Vettel goes quickest in S1, but a minor mistake means a PB in S2. At the line he posts 17.954 to go second, the German really struggling in the final sector.

Raikkonen's lap is over before it's begun, the Finn locking up at T1 and ruining another set of tyres. "I've got quite a bad vibration," confirms the Finn.

No such issues for Leclerc, who posts PBs in all three sectors to go ninth (19.024).

Next time around, Raikkonen improves to fourth with an 18.133, albeit 0.696s off Verstappen's ultrasoft pace.

Grosjean goes sixth (18.733) on the hypers as Sainz bangs in a 17.953 to go second. Renault continuing to look very, very strong here.

"The tyres were absolutely nowhere," claims Magnussen having only improved to 17th on the hypers (19.995). That said, teammate Grosjean is currently 10th (18.733).

Bottas can only manage eighth (18.140), as he gets worryingly close to the wall in the final corner.

Verstappen is among the last to switch to the hypers. However, he can only manage a PB in S1, before going quickest in S2. Strongest again in S3, he crosses the line at 16.720.

All eyes on Ricciardo, who heads out on the hypers, leaving Vandoorne as the only driver still to make the switch.

Asked how it was, Verstappen reports: "All over the pace, especially the engine, not doing what it was supposed to do." The boy is never satisfied.

Ricciardo posts PBs in the first two sectors, finally crossing the line at 16.873, just 0.153s down on his teammate as the Bulls enjoy a 1.2s advantage over third-placed Sainz.

At half-time, as attention switches to race simulations, it's: Verstappen, Ricciardo, Sainz, Vettel, Hulkenberg, Hartley, Hamilton, Raikkonen, Bottas and Perez.

While most are now on their race sims, with 35:00 remaining, Vandoorne heads out on hypers for his qualifying sim. Though Renault powered cars fill four of the top five places, the similarly-powered McLaren pair are 15th (Vandoorne) and 19th (Alonso).

"That's all I have, I'm flat-out," sighs Vettel.

Meanwhile...

"Something's not right with the car, man" claims Hamilton. The Briton subsequently attempts to negotiate a clearly struggling Magnussen who seems unable to get his car to do what he wants it to do.

Mercedes has Hamilton on the hypers and teammate Bottas on the ultras.

"I've got a 'PU hot' warning," reveals Ricciardo, "it's been there for a while."

Alonso does well to keep it out of the wall following a long ride over the grass after running out of road following a brief battle with Ocon.

"This tyre is dead, man," insists Hamilton.

Clearly, Red Bull is looking very good here, with Ferrari, particularly, Vettel having a slight edge over Mercedes.

"I think I will box," says Alonso. "Fernando, I'd like you to stay out, please stay out," comes the response.

Meanwhile, Verstappen has stopped at the final corner, his session over. As he climbs from the car, out come the yellows.

Replay shows a total loss of power with even the dash display disappearing.

And it was all going so well.

Having had a nice two from Bottas, Vettel pulls out of the slipstream and sweeps past the Mercedes. Both have completed an impressive 40 laps.

Before his shut down, Verstappen's run saw the Red Bull driver lapping at 22.9, compared to Ricciardo's 23.3. Vettel was managing 24s while Hamilton was lapping at 24.6.

As the session ends... the camera cuts to the Red Bull garage where Verstappen is in conversation with Helmut Marko. Oh to be a fly...

Verstappen is quickest, ahead of Ricciardo, Sainz, Vettel, Hulkenberg, Hartley, Hamilton, Raikkonen, Bottas and Perez.

Ocon is eleventh, ahead of Grosjean, Leclerc, Gasly, Vandoorne, Stroll, Ericsson, Sirotkin, Alonso and Magnussen.

Check out our Friday gallery from Mexico City, here.