Rodolfo Gonzalez said his aim for his maiden Formula 1 test with Lotus in Abu Dhabi today was to do an 'intelligent' job for the team, before being given clearance to go for fast times tomorrow.
The Venezualen GP2 driver was 13th quickest today.
"It's a big step from GP2 to Formula 1," Gonzalez acknowledged.
"Mike [Gascoyne] said to me this morning 'today you won't show me that you're ready for Formula 1, but you can show me that you're not ready for Formula 1... So try to do an intelligent job - you don't have to impress anybody, you've already impressed us and that's why you're here.'
"So that's what I tried to do. I went from less to more. It didn't feel such a big jump from GP2 to Formula 1, it was just the speed on the straight, which I got used to pretty quickly, and the downforce.
"We did high fuel runs all day, we put on a good set of tyres at the end of the day, with a reasonable amount of fuel, and the team are happy with the time we did because they know how much fuel we had.
"So I think overall it was a very positive day."
He admitted that the physical demands of stepping up to the F1 car had been tough on his neck in particular.
"I did 83 laps today. By the 80th lap, it was finished..." he said. "I had another set of tyres to go, but I told the team there was no point because I knew I could improve in the driving, but my neck was finished."
Gonzalez will drive again tomorrow morning before handing over to Vladimir Arabadzhiev. He will be given softer tyres and allowed to try qualifying-style laps in that session.
"We're going to do low-fuel runs tomorrow, so the target is to go as fast as we can and find a little bit more time," Gonzalez said.
"We're going to do some set-up changes, and there's a little compromise with my driving - I need to be a bit smoother with the steering wheel in some corners to not induce so much understeer in the car.
"I'm looking forward to having really soft tyres tomorrow and low fuel and seeing how that feels."