- Sebastian Vettel fastest in practice ahead of Korean Grand Prix
- The German is second in the world championship, four points behind Fernando Alonso
- Ferrari's Alonso third fastest, behind Vettel's Red Bull teammate Mark Webber in second
- Michael Schumacher reprimanded by stewards in afternoon session
Sebastian Vettel's late-season charge towards a third consecutive Formula One world championship continued Friday as he set the pace in practice ahead of the Korean Grand Prix.
The Red Bull driver, the sport's youngest ever double title winner, posted a lap of one minute and 38.832 seconds in Yeongnam, three one hundredths of a seconds faster than his Australian teammate Mark Webber.
"We had a pretty good program for today and I think both of us managed to get the most out of it," the 25-year-old told F1's official website. "We'll have a look where we can improve tonight in different areas.
"So far so good, we have good information and the guys will now get on with the job tonight."
The German has won back-to-back races, closing the gap on current championship leader Fernando Alonso to just four points with five rounds remaining in the 2012 season.
Ferrari's Alonso, also a two-time world champion, was third fastest, saying the track conditions differed across the morning and afternoon sessions.
"The track improved a great deal from one session to the next: it's a phenomenon that's particularly accentuated here, because there's hardly any racing on this track and this morning, it was particularly dirty," the Spaniard explained.
"Let's hope the situation improves for tomorrow because it's always more fun driving when the track offers at least some grip."
McLaren's Lewis Hamilton apologized to his teammate Jenson Button earlier this week after accusing his fellow Briton of "unfollowing" him on Twitter.
Hamilton, who will join Mercedes in 2013, failed to complete a lap on the faster, slick tires, but remained hopeful McLaren could compete in Sunday's race.
"The Red Bulls look pretty quick, but Jenson wasn't that far off their pace this afternoon," Hamilton, eighth fastest on the day with Button fourth, explained.
"So that's good. We'll make some changes to the balance overnight, and hopefully we'll be in better shape for tomorrow.
"As I say, this afternoon Jenson showed that our car has pace; all we need to do is fully extract it. If we can improve the balance overnight, I think we can be competitive."
Seven-time champion Michael Schumacher was an encouraging fifth for Mercedes in the afternoon, but the 43-year-old German, who is to retire at the end of the season for a second time, also earned a reprimand from stewards for holding up the HRT pair of Pedro de la Rosa and Narain Karthikeyan during the session.