Nico Rosberg reckons the Yeongam circuit "suits" his W03 despite overheating the rear tyres.
Rosberg and his team-mate Michael Schumacher finished Friday's practices for the Korean Grand Prix seventh and fifth on the timesheets respectively.
Mixing it behind the Red Bulls with the Ferraris and McLarens, Rosberg says Mercedes have cause to be happy.
"It's been a good day for us; I think we've made some good progress," said the German.
"Michael had some new things on the car - some small things to try - and they seemed to work well.
So I think maybe a little bit of an upward trend for us today and going in the right direction on this track [which] I think suits us a little bit more."
As for tyre wear, Rosberg believes Mercedes are looking good despite a bit of overheating of his rear Pirellis.
"Tyre-wise it's wearing quite well. I mean we're overheating [the tyres] a little bit in the long run, but it's okay. I think this circuit suits our car quite well."
Vettel Leads Red Bull 1-2 In Practice Two