Kimi Raikkonen's lap of 1 min, 17.221 secs Friday came within 0.039 sec of the track record set by Ferrari teammate Sebastian Vettel Thursday. He was briefly second on the time sheets, but fell afoul of the track limits rules and promptly had his time deleted.
Sergey Sirotkin (Williams) completed the top 10 after handing over to Lance Stroll for the final few hours, with the Canadian again setting the slowest of the day behind Hamilton using softs.
The laps left Ferrari significantly clear of the field, albeit with the caveat that reigning World Champions Mercedes did not use Pirelli's new-for-2018 pink-ringed compound.
Defending champion Lewis Hamilton and MercedesAMG teammate Valtteri Bottas focused on running race simulations for a 2nd day running Friday. Castroneves was moved out of Penske's IndyCar organization at the end of last season and now leads its new sports car program.
"It was the first time I ran the car in [race] conditions. I think very quickly we are going to get back to normal".
It looked like it would be a poor day for Alonso, who was forced to a stop on the gravel just after Turn 7 as familiar problems re-emerged.
McLaren as the wild card in the pack as a result of their unreliability but with the team still confident their chassis and engine package can deliver a profitable season once a happy compromise is achieved between the Renault unit and the MCL33's tight packaging. He had a troubled morning, spending the majority of the session in the garage with a gearbox issue.
F1 testing: Ferrari quickest, Mercedes super strong, and there is hope for Fernando Alonso
Ferrari also showed good reliability, running more than 920 laps in total.
The same can be said of Hamilton's team-mate Bottas.
But with the mountings and brackets that are needed to secure this, the weight of the car could be heavier again - meaning teams will have to find ways to save weight in other areas to boost performance. I think we have made improvements. The MCL33's five breakdowns were five more than Mercedes and Ferrari combined.
Two weeks of Formula 1 testing of 2018 season are finally over. We adapt. We move on with life. "Testing done. Let's go racing", he said.
After yesterday's impressive run with Kevin Magnussen, Haas upheld its form, with Romain Grosjean slotting in nicely behind Raikkonen, and comfortably ahead of Brendon Hartley's Toro Rosso in third.
"It's a very similar situation to what we've got at Ferrari where Sebastian Vettel is kind of the No 1 driver, whether officially or not, and he's voiced his support for Kimi Raikkonen to stay there".