Sebastian Vettel admits the tire situation in Korea is a concern, with the high wear set to mean drivers will have to stop several times during the race.
"We can do maximum five [pit stops] and that is all the tires we have, then maybe we will have a set of inters again to cross the checkered flag," joked Vettel after Friday's practice. "Maybe it turns out to be better than expected or worse. It is quite a tough track on tires. I think even with long straights, there is hardly any rest after that. So it's not that easy.
"Everything we learned today is not worth a lot for the next two days but the car feels alright so that is most important."
Pirelli has brought the soft and the super-soft tires for the Korean event, something that is also likely to mean drivers will save sets during qualifying.
Vettel finished the day as third quickest behind the two McLarens, which dominated the running in the wet this afternoon. Although the German Red Bull driver was nearly two seconds off the pace, he admitted he was not too worried.
"I don't think it is tougher than the other weekends," he added. "It would be bad if the others had gone around with half the throttle in the other races, but I don't expect it to be more difficult than other races.
"We will see who is more competitive. In the conditions this afternoon McLaren looked very strong but we have seen that a couple of times on a Friday so it is hard to say."