Rain and fog effectively spoiled the final day of the three-day test, with the worsening conditions sealing Espargaro and Vinales' places at the top of the timesheets.
The pair also topped their respective categories in pre-season testing at Valencia one week ago.
Espargaro, runner-up to Marc Marquez in last year's Moto2 championship, went quickest in all three sessions on the second day.
The Pons rider eventually worked his way down to a 1m42.332s, leaving him just under three tenths of a second clear of Italtrans rider Takaaki Nakagami in second.
Marc VDS's Scott Redding, fourth in last year's championship, finished third fastest but more than half a second down on Espargaro.
Julian Simon on the second Italtrans and Aspar rider Nicolas Terol rounded out the top five.
Last year's Moto3 champion Sandro Cortese finished 18th fastest, just ahead of Ratthapark Wilairot, who crashed with Thomas Luthi in the Valencia test.
Luthi will miss the first two rounds of the championship after suffering multiple fractures on his arm and shoulder.
Vinales meanwhile went fastest in what proved to be the critical Moto3 session on the second afternoon, before the conditions worsened.
The Laglisse rider edged out Monlau's Alex Rins by just six thousandths of a second, while Ajo's Luis Salom made it a repeat of the Valencia top three by sealing third.
Jonas Folger was the only other man to get within one second of Vinales, giving KTM a lockout of the top four positions.
Miguel Oliviera continued Mahindra's encouraging start to 2013 by finishing fifth, just ahead of CIP's Juanfran Guevara, who finshed as the fastest rookie.
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