"It seems that Renault is having a few problems. Sebastian Vettel's Red Bull was the only Renault-engined car we saw on track for much of today, with both Caterham and Scuderia Toro Rosso being sat in the garage for a long time.
"Red Bull is the works Renault team, so it's conceivable it is doing some troubleshooting work. Yesterday, the Caterham only managed one lap before stopping with an electrical problem while the Toro Rosso had serious trouble with the engine mapping, which Jean-Eric Vergne said led to the car "oscillating". You could see what he meant as it juddered up the pitlane and out onto the track.
"Today, the Mercedes cars are averaging 14 laps per car and the Ferrari-powered machines 24 laps. Vettel has done eight laps, which means the three Renault-engined machines are averaging less than three laps each for over four hours of running."