Both Pastor Maldonado and Bruno Senna lamented the slippery surface of the Circuit of the Americas.
"The circuit is really nice and it was fun to drive. It was very slippery, particularly this morning on the hard tyres, but it’s the same for everybody. We struggled a bit today with the car which we need to look at tonight in order to be ready for tomorrow", said Maldonado, who stopped at the end of FP2 with an engine leak.
Senna was eighth in second practice.
"The track is really challenging so it was great to gets lots of running in today. It’s very fast and flowing, and also a bit slippery at the moment but the grip is coming", he said.
"It was a tough session as there is a lot to get used to with the car and the tyres. We need to keep pushing to try to understand the car better and improve to make sure we are in the points this weekend".