I would think most people would already have arrived in the city for the Formula1, with not so many arriving same day by air. I don't live in S.P. and so can't comment on any extra vehicle traffic between GRU and CGH on F1 day. Afaik Interlagos is not near those parts of the city that you pass through to get between airports; it is kind of south. GRU is kind of north-east. Congonhas is in the city center (look for the Brooklin/Campo Belo/Moema neighborhoods on a map).

And here's a map:
https://maps.google.com.br/maps/ms?i...e5585e86cfe9b4