Max Verstappen and Daniel Ricciardo continued to dominate the standings as a very mixed up order emerged in Practice 2 for the Mexican Grand Prix.
With the Pirelli tyres continue to struggle for grip and durability there was a big variation in those teams getting it right and those who are not with Mercedes and Ferrari very much falling into the latter.
There is no problem at least pace-wise at Red Bull, however, with Verstappen posting a 1m16.720s on the Hypersoft compound to lead his Australian teammate by just a tenth-and-a-half.
On reliability though, concerns remain with Ricciardo picking up a 'Hot PU' warning and Max having to stop during the race simulation with possible engine trouble.
The pair did finish a second clear of Carlos Sainz in third for Renault, as the French manufacturer's strong pace from the morning also remained with Nico Hulkenberg fifth. Brendon Hartley was another midfield runner punching well above his weight in sixth.
As for the usual pacesetters, Sebastian Vettel simply had no confidence in the corners in third albeit only 0.001s behind Sainz but things were worse for championship leader Lewis Hamilton as he sat down in seventh and simply reported; "something's not right with the car" over the radio.
Their respective teammates Kimi Raikkonen and Valtteri Bottas ran eighth and ninth with Sergio Perez giving the Mexican crowd something to cheer in 10th for Force India.
The Ferrari-powered midfield teams have some work to do with Romain Grosjean 12th for Haas and Charles Leclerc 13th in his Sauber, the difference of the old Honda engine is also noticeable with Pierre Gasly a full second behind his teammate in P14.
McLaren bucked the trend of Renault-powered cars running well with Stoffel Vandoorne 15th and half a second clear of teammate Fernando Alonso, although he did post his time a little later than his Spanish teammate.
The British team's fight again looks to be with Williams and Marcus Ericsson at the back of the grid but it was Kevin Magnussen who finished slowest overall in the Haas.
A full look at the Practice 2 results can be seen below:
At the end of play on Friday though, the big question is can Mercedes and Ferrari find solutions to the tyre problems which seemingly leave them trailing massively behind Red Bull and also suffering from major tyre wear.
Or do they need to with the Milton Keynes outfit clearly faster but suffering from a lot of nervousness over reliability as the memories of 2017 and now the long-run issues in second practice show just how fragile the Renault engines are.
Quite the weekend in prospect.
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