Sebastian Vettel's running during the Silverstone in-season test was hampered by the need to change his Renault engine on Wednesday.

Although he completed 76 laps, Vettel was 4.1s off the ultimate pace on the final day of testing as Red Bull tested tyres for Pirelli. However, once the Pirelli program is completed then teams are able to carry out their own work but Vettel said the need to change the engine had cost Red Bull the opportunity to do so.

"It was a tyre test day so we did all the work for Pirelli," Vettel said. "It's obviously a shame that we had to change the engine, I lost some track time but overall the boys did a good job by changing the engine quickly and we had a solid two hours at the end."

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Looking ahead to Germany, Vettel said he was unsure how competitive Red Bull is likely to be.

"It's difficult to say, it has been a little bit up and down this year. Obviously we hope for a smooth weekend without any problems and then we will try to get the best out of myself, out of the car and it would be very special to finish on the podium there."

When it was put to Vettel that the FIA's potential ban of interconnected suspension systems could help Red Bull close the gap to Mercedes, he admitted he expected it to impact on the competitive order.

"Obviously we know what we are running, we don't know what they are running. I think it's pretty clear what the FIA has said so probably some teams will be more affected and others less."