Team official Dr Helmut Marko has insisted that the RB12 is "the best chassis Red Bull has ever built".
On day two, Daniel Ricciardo was second best behind Ferrari's Sebastian Vettel, on the same purple-walled 'ultra soft' tyres.
"The fuel, [and] which engine mode [Ferrari] were in, we don't know," said Marko when asked about the seven-tenths deficit. "We are still conservative.
"But our car was quick right away and reacts logically to each setup change."
The Austrian also sounds upbeat about the engine situation, adding: "After the experiences of the last two years, it is completely unfamiliar to us to be getting so many kilometres under the belt."
There were some problems when Daniil Kvyat got his first taste on Wednesday, but Marko is still complimentary of the work Renault has done.
"Clear progress can be seen," he said. "It goes in the right direction.
"It is good that they have made Remi Taffin the boss. He is a practical man who saw the problems on track and knows what needs to be done."
Red Bull finished fourth in last year's constructors' championship.
