Nick Heidfeld lamented the track time lost in Thursday's practice for the Monaco Grand Prix after being forced to replace his engine.
The BMW Sauber driver stopped on track following a sudden loss of power during first practice.
Heidfeld managed just 13 laps in the morning, but enjoyed a more productive session in the afternoon, covering 44 on his way to the 11th fastest time.
"Of course the failure cost us running time and data, but we still managed to make several changes to the car for the second session," he said.
"It was a general improvement. Taking into account it is Monaco, I would say my car is very driveable."
Teammate Robert Kubica had a trouble-free day and posted the sixth quickest time.
"The two practice sessions were quite okay today," he said. "It was a very busy Thursday and we covered a lot of laps. We now have to see how we can improve the car for Saturday."