World Championship leader Sebastian Vettel admitted there was little to be learned during Friday practice at Spa, with only a few minutes of dry running across the two sessions.
Repeated showers meant only the opening minutes of practice one and a 15-minute spell in the middle of practice two were dry enough for slick tires. Vettel's Red Bull was fourth in practice one and 10th in the second session.
"I think I learned as much as you today, I don't know. Maybe a bit more," Vettel told reporters. "It was quite tricky because the weather changed all the time and it is a shame in wet conditions that we only have one free set of inters.
"For the rest of the weekend, you can imagine the weather forecast and the rain is absolutely possible, the question is how much. We try to save as much as we can, so we don't want to ruin the tires we have for Saturday and Sunday."
Vettel said he only managed one full run on a dry track.
"We had a little bit of running in the dry, on the front wing we got a decent result on that, but that was the only run we had in dry conditions," he said. "Lap times are difficult to judge today, and difficult to know where we are, but the car feels OK. Let's see what we can do."