The multiple world champion, who won gold in the two-man bobsleigh on Monday, steered his sled to a 0.29 seconds lead over Won Yun-jong's South Korean team, which enjoyed the support of a raucous hometown crowd at the Olympic Sliding Centre.
Germany's Nico Walther finished in third, 0.35 seconds behind his countryman and a slim 0.06 seconds behind the South Koreans.
Friedrich's German team eases to four-man gold, Team GB struggle
Justin Kripps, who tied with Friedrich for gold in the two-man, carried his Canadian team to fourth, 0.58 seconds off the lead, with Germany's Johannes Lochner lurking in fifth, 0.66 seconds back.
It was a good day for Codie Bascue's American team, who saw their sled jump from 12th to ninth position, 0.88 seconds behind Friedrich ahead of Sunday's final.
GB’s Lamin Deen, Toby Olubi, Ben Simons and Andrew Matthews went down in 49.44 and 49.45 to finish 1.35 seconds behind, while team-mates Brad Hall, Joel Fearon, Nick Gleeson and Greg Cackett were just 0.10 seconds behind after times of 49.25 and 49.68.