Romain Grosjean has declared he is a "happy driver" following his first day in the new Lotus E23.
Replacing team-mate Pastor Maldonado for the final day of testing at Jerez, Grosjean covered 53 laps with a best time of 1:23.802.
And although that was almost three seconds slower than Kimi Raikkonen's P1 time, the Frenchman is confident his new challenger and its Mercedes engine are a step up on last year's car.
"My first impressions of the E23 Hybrid are good," he said. "Both the power unit and the chassis are going in the right direction.
"I completed over fifty laps today and I can honestly say that all of them were enjoyable to drive. The team has made very good progress if you consider where we were this time last year.
"It's a very good start and I’m a happy driver."
The day, though, was not without problems as Grosjean's running came to an early end after power unit running data showed that a problem was developing.
But despite technical director Nick Chester says it has been a positive outing for the team.
"Even though it’s been an early end to our final day of running in Jerez, we’ve made fantastic progress over the past few days,he said.
"We fired up the E23 Hybrid for the first time at Enstone last Saturday night, ran it for the first time on Monday, then completed a very useful haul of laps over the course of the test.
"Both Romain and Pastor have declared themselves happy with the car and we have a clear direction for future developments.
"Today we finished early as analysis of power unit running data suggested a problem was developing. The power unit will now return to Brixworth for a full investigation.
"We have a busy week ahead of us at Enstone to make further progress with the E23 and we’re particularly looking forward to the next test in Barcelona."