The fastest time of the morning wasn't improved upon in the afternoon, even though reigning World Champion Lewis Hamilton came within 3 thousandths of the Ferrari pace setter.
By the time that Hamilton went considerably faster than anything he had managed earlier on in testing, Ferrari was already sidelined and packing up. The SF90 had suffered an electrical issue shortly before halfway in the afternoon session, and it was soon obvious that it would take too long to get the car running again.
Red Bull also hit problems as Verstappen continued to struggle with gearbox issues on the RB15. The gremlins prevented the Dutchman to add any lap to his morning tally.
It was about 90 to 60 minutes from the end that Hamilton finally improved his pace, gradually improving on the C3 compound, before a switch to the faster C4 got him the pace to set laptime comparable to what Vettel had done. A further switch to the even softer C5 compound didn't yield any further improvement, as was the case for most cars at Barcelona.