Sebastian Vettel was hesitant to predict whether current champions Red Bull can challenge runaway leaders Mercedes on a consistent basis in 2015.
Vettel has endured a troublesome season in the RB10 and has finished on the podium just twice in the first nine races.
Red Bull has been plagued by Power Unit issues for much of the year and Vettel is unsure as to whether the squad can catch up with Mercedes, even by next season.
"It’s difficult to say, right now obviously the gap is very big and we didn’t really close it since race one, we’re waiting for bigger steps to come to close the gap more, I think at the end of the season we can judge a bit better what to do in the winter," he said.
Vettel was ninth quickest on the second day of the third in-season test at Silverstone and spent much of the day testing tyres in association with Pirelli.
"Tyre test today so we did the work for Pirelli, obviously a shame we had to change the engine," he said. "They did a good job to change it quickly and we had a good two hours at the end. [They were] different tyres for next year, [so] no impact on this year."
Vettel is hopeful that he can challenge for the top three positions at his home race in Germany next weekend.
"It has been a little bit up and down this year," he said. "We hope for a smooth weekend without any problems and try and get the best out of myself, out of the car as it would be very special to finish on the podium there."