On another sunny day at St. Moritz, the American found speed that eluded her rivals to clock 1 minute, 43.65 seconds on the relatively flat 1.57-mile track.
"I'm extremely happy with the win," said Vonn, whose eighth World Cup victory this season extended her lead in the overall and downhill standings. "It's been an amazing year so far."
Maria Hoefl-Riesch of Germany, the defending overall champion, was runner-up. Tina Weirather of Liechenstein was third, 1.47 behind Vonn.
Vonn's closest challenger in the overall standings, Tina Maze of Slovenia, was fourth, 1.65 seconds back.
With 100 World Cup points for victory, Vonn leads Maze by 352 with half the season's scheduled races completed.
Barring injury, Vonn seems unstoppable in her quest to reclaim the title she lost last year after winning the giant crystal globe trophy for three straight years.
"Last year I had eight wins for the entire season. I already have eight this year and it's only the end of January," she said. "I'm never tired of winning and I'm never tired of skiing."
Vonn, who won the super-combined event here Friday, got her 49th career World Cup victory and 24th in downhill. It was her third success in Alpine skiing's glamor event this season.
Her margin Saturday was stunning for any racer yet it was her narrowest downhill victory this season. In her two wins at Lake Louise, Alberta, last month, the runners-up were France's Marie Marchand-Arvier and Weirather by 1.68 and 1.95, respectively.
"It's a weird feeling," Vonn said. "I just feel so relaxed and enjoying what I do so much."
Hoefl-Riesch said she was happy just to finish second behind Vonn, matching her best result in what has been a difficult season. She stands third overall, yet with barely half of Vonn's points total.
"It seems like Lindsey is really hard to beat. She's skiing perfect," said the reigning overall champion, who hugged Vonn standing in the leader's box after skiing immediately after her friend.
Weirather, who took the early lead, laughed after being asked to explain the feeling watching Vonn attack her time.
"It's strange because you know she is going to be fast and you are waiting to see just how much it is," Weirather said.
The 22-year-old Weirather moved up to second in the downhill standings, 190 points behind Vonn with four races remaining.
On a good day for the American team, Julia Mancuso tied for fifth place, Leanne Smith finished seventh and Laurenne Ross was 16th.
Mancuso was faster than Vonn at the first intermediate time check, and seemed poised for at least a podium finish until hitting a tough line at a traverse approaching a tight left hand turn. Mancuso moved up one place to fifth in the downhill standings.
Smith got her career-best World Cup result, having been eighth in a super-G one year ago at Cortina d'Ampezzo, Italy.
"It was exactly how I wanted to ski. I executed my plan," said Smith, who had been fourth in Friday's downhill portion.
Vonn can complete a St. Moritz treble in a super-combined scheduled Sunday, which includes super-G and slalom legs.
Success at the ritzy Swiss resort was a long time coming for Vonn, who was 25 when first winning here two years ago in a super-G. Saturday's victory was her first in downhill here on the seventh attempt.
Vonn has now won the event at 11 different World Cup venues.