Track evolution proved to be the defining characteristic of the first day of running at the famous Interlagos venue in Sao Paulo, with the circuit having been recently resurfaced and a new pit lane entry installed as well.

The first day took place in hot conditions, with ambient and track temperatures peaking at 34 and 57 degrees centigrade respectively. However, these conditions are far from guaranteed to remain for the rest of the weekend, with the weather forecast predicting intermittent rain: particularly during qualifying. There was a difference of more than 20 degrees in average track temperature between the morning and afternoon sessions, partially accounting for the difference in lap times between the two sessions.

This means that the teams will have to be prepared for a wide variety of conditions, so they concentrated today on gathering as much data as possible on different fuel loads, using both nominated compounds: P Zero White medium and P Zero Yellow soft.

Mercedes finished first and second in each of the two sessions, with Nico Rosberg leading Lewis Hamilton on both occasions. In the morning Rosberg set his fastest time on the medium tyre, before using the soft tyre in the afternoon to go six-tenths of a second faster.

On average, there is a performance gap of around 0.8 to 1.0 seconds between the two nominated compounds, but this will probably come down as the track evolves further.

Paul Hembery: "We started the day seeing a very high influence from the new surface and its interaction with the tyre, but this was changing rapidly as the sessions went on, with strong track evolution. We're also seeing that rear tyre is the limiting factor here, and on some occasions, with close to 60 degrees of track temperature, there was some blistering - which is what we envisaged bringing the softer tyre here, when conditions were hot. We've got about one second of performance difference between the two compounds, but due to red flag interruptions today we still don't have a clear indication of the levels of true degradation we're ultimately going to see. So tomorrow is set to be a very important session."

Check out our Friday gallery, here.