The Frenchman was the first man to try out the new Lotus E21, which the team hopes will be enough to lift it into top three contention this year.
And although Grosjean ended up nine tenths of a second behind pacesetter Jenson Button, he was hugely encouraged by what he discovered.
When asked if he had got what he had hoped to from the car, Grosjean said: "Yes, but I would say even better to be honest.
"The first feelings were very, very good. It's been a long time since we drove last time, but it has also been a short time at the same time.
"Honestly, three laps in and the car was already on the pace and the car was good without any set-up work."
The new Lotus E21 is an evolutionary design from last year's car, but Grosjean says he already feels progress has been made.
"I think it's a good step forward, compared to where we were last year - which was already a good starting point," he said.
"There was no issue with the car today; we could do 55 laps which were all pretty quick, and that's a good point."