Sergio Perez - 4th/8th: "Today we had a very good first session, but a more difficult second session.
"That was a bit of a surprise for us, because this morning the car felt very strong and very fast, and I was very happy with its balance. But this afternoon, as I say, it was a little less consistent.
"However, we've got a lot of information to analyse now, so as to understand what's going on with the car, in an effort to try to improve it and hopefully do a good job for tomorrow and Sunday.
"Hopefully, the weather will help us, because I personally would prefer there to be wet or variable conditions, which we know is always possible here at Spa!"
Jenson Button - 14th/15th: "For me, FP1 was very good, and I was very happy with the car. The balance was good and I think our pace was good, too. I didn't push very hard in the wet sectors, but in the dry as I say it felt very good.
"This afternoon, however, it felt different. It's obviously a result of the warmer temperatures, and perhaps the wind also, so we've got a lot of work to do to understand why that is. Hopefully, we'll work it all out and things will be better for us by tomorrow.
"Having said all that, it's great to be back at Spa - the circuit is simply stunning! It's one of the best circuits for a driver, so fast and flowing. You have true racing fans here too, which is fantastic to see.
"OK, the circuit is a bit unforgiving, but in a way I don't mind that. I think we've lost a bit of that element with some of the newer circuits we've seen arrive on the calendar over the past few years. The old classics are the ones that really remind me why I love this sport so much: here, Monza, Suzuka etc."
Martin Whitmarsh - team principal: "Like most grand prix Fridays, today was a day spent data-gathering, running experiments, and working towards finding optimal set-ups for the rest of the weekend.
"As a result, we've duly gathered a lot of data, which we'll number-crunch this evening in an effort to prepare our cars for qualifying tomorrow.
"As ever here at Spa, though, the weather will be an unpredictable factor both tomorrow and on race day, but it'll be the same for everyone.
"Reverting to today, then, our drivers appeared to prefer our car's balance this morning, in FP1, when the track surface was slippery. This afternoon, in FP2, when it was warmer and drier, they were rather less comfortable.
"But no one can claim with any confidence that he or she can make accurate weather forecasts about the Ardennes micro-climate, so let's see what the next days bring."