Heikki Kovalainen delivered a near-perfect first day's driving on his return to Lotus as a two-race stand-in on Friday.
He completed opening free practice for the United States Grand Prix in fifth place.
Lotus technical director Nick Chester said the team were impressed by his first day as a replacement for Ferrari-bound, fellow-Finn Kimi Raikkonen.
Raikkonen was in France where he underwent successful back surgery in Strasboug.
"We feel he's done a brilliant job today, particularly with all the procedures and getting used to driving a new car," said Chester.
"We felt it might take a little bit of time but actually straight away in P1 he was already looking after the car very well.
"He got into P2, fifth quickest, good long runs, I think he's done a great job today."
Kovalainen said his first day back with Lotus was "pretty smooth".
He added: "We've had no major issues on track today and we just need to keep chipping away to see how good we can get the car for tomorrow and Sunday.
"We lost a bit of track time in the morning, but the car balance was reasonably good straight away. I was able to settle in and work immediately on the set-up and tyre work.
"All the procedures and routines are quite similar up and down the pit lane, plus I'm familiar with all the systems from driving with a Renault engine (at Caterham) already this year, and previously, so it was a pretty straightforward day."