With teams and drivers having to work hard to find the right balance between straight line speed and generating sufficient grip for cornering, Valtteri Bottas has decided that the need for speed has to come first.
The Mercedes driver was quickest in the morning session, and ended the day just 0.041s off the pace of Red Bull's Max Verstappen in the afternoon session.
"It didn't look too bad today with the pace in the short runs and the long runs," he said afterwards. "It was pretty decent.
"[It's] always tricky to compare in detail from the practice, but at least the feeling is good so that's a positive," he added.
"We definitely seemed quite fast on the straight line - maybe less so in Sector 2 where the corners are - but for me, for the race, it's important to be quick in Sector 1 and Sector 3 to make the overtakes.
However the Finn acknowledged that the weather could force the team to change its plans, as rain would make raw speed less of a priority compared to grip meaning that a higher downforce setting will be crucial.
"If it rains, you want more downforce," he agreed. "It's going to be a key decision for what we choose for qualifying. Session by session, we need to see how it is going to look.
"As we saw from the timesheets, it's going to be very close with Red Bull once again so we'll look into the detail tonight and see what marginal gains we can find."
Mercedes trackside engineering director Andrew Shovlin said he was pleased with the progress made so far at Spa.
"We've had a pretty clean day overall," he said. "We've made good use of the sessions and have ended up with a reasonable balance.
"It's hard to know quite where we stand. The circuit is very power sensitive so going up and down on modes can give big swings in lap time, but the car seems to be working as it should and it looks like we're there or thereabouts on pace.
There's a bit more to find on the balance, and Lewis had some vibrations on the long run that won't have helped, but hopefully we can make some further progress with the car overnight."
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