Sebastian Vettel said he was pleased to lead the way after the first day of running in Korea, although the German admitted it was close towards the head of the pack.
Vettel edged out team-mate Mark Webber to lead the way after Friday practice, ending the second session just 0.032secs ahead of the Australian as the Red Bull duo ended up first and second on the times.
The German goes into this weekend chasing his third successive win as he seeks to try and edge ahead of Fernando Alonso in the standings, and despite being quickest on track, he said the team needed to improve ahead of qualifying to remain out front.
“All in all we can be quite happy, but I think it looks extremely tight,” he said. “I'm not happy with every run we had today, but I think the track was changing quite a lot this morning, it was better than we expected.
“This afternoon it was quite slippery to start with, but then I think it got a little bit better so, all in all the car felt alright and now we see what we can do for tomorrow. I think we have to improve ourselves to match the others.”
Webber too was also pleased with the day had gone but agreed that the team needed to look into how to improve overnight.
“We had a pretty good programme for today and I think both of us managed to get the most out of it,” he said. “We'll have a look where we can improve tonight in different areas; it's always a compromise on a track like this with a bit of top speed in the first sector, then the last sector is pretty twisty in terms of rhythm – it's a bit like Budapest, so you need a bit of downforce there. So far so good, we have good information and the guys will now get on with the job tonight.”