Sebastian Vettel and Mark Webber were first and second fastest in both Friday sessions, with the often-cautious duo both expressing delight with the Red Bull's pace at the end of the day.
Grosjean was best of the rest and showed encouraging long-run pace. He thinks Lotus's traditional improvement over the course of a weekend means the race is still open.
"They are quick but they are very often very quick so I am not really surprised by their speed," he said.
"We need to see on Sunday what it gives and what we can get.
"We mainly focused on trying to see what the difference was with the new Pirelli tyres to see if we had much to change.
"It appears that it is not night and day so it helped us that we didn't have to change everything.
"We will try to get the best of everything we found to bring it tomorrow and then fine-tune the car for qualifying. Hopefully that will be good for the race."
Asked if Lotus was expecting the rising temperatures to play to its advantage, as is often the case, Grosjean replied: "It may change things. I hope so. The answer is on Sunday."
Raikkonen did not get many clear laps in second practice but said he took little notice of Red Bull's Friday dominance anyway.
"We had some issues at the beginning of the session and we lost a little bit of time, we didn't get the lap time on the new tyres because of traffic and then we didn't enough long run to know," he said of his pace.
"I think it was a bit difficult today, too much understeer and we have to work on certain things. It is not an awful lot - we'll just try to find a bit of a better solution.
"Tomorrow is a different day and we'll try to do our best; if on Fridays you are fast it doesn't mean it will be like that on Saturdays."
- Motor Racing
- Sebastian Vettel