Ryder Cup players dominating
Jimenez had conceded a one-shot lead to Spanish compatriot Garcia at the end of the second round, but his better back nine en route to a third-round 5-under-par 66 helped him regain the lead at 15-under-par 198.
Garcia increased his overnight advantage with an opening eagle. Three back-nine bogeys let in first European wild card Donald and Jimenez, however.
Garcia made a spirited recovery but came up a stroke short with a 68, and Briton Donald conceded a share of first place overnight by bogeying the last for an otherwise sparkling 65.
Jimenez is bidding for a fifth win of the year and successive tour titles. He is eyeing a record-tying six wins of the year, matching the feats of, among others, his compatriot and inspiration Seve Ballesteros.
"If I win my fifth title, then I will be trying for the six, why not?" Jimenez said.
Being in contention so often is not sapping his energy, either, he insisted. Garcia had tried to persuade Jimenez not to play his fifth successive event next week in case it tired him for the following week's Ryder Cup match.
"I feel strong. I'm doing the right thing. I don't feel I need to take a break," Jimenez said. "I have my family with me here and I'm nice and relaxed.
"It's like being on holiday, and it's good when you can be on holiday and make a good profit."
Donald was disappointed at not sitting alongside Jimenez on the leaderboard after an unusually high bounce on the last that took his ball off the green.
Defending champion Ernie Els had complained earlier that the greens should have been watered, and Donald agreed.
"Some of the greens are inconsistent," the 26-year-old Briton said. "But I'm right where I need to be. It's nice to shoot three good rounds and validate Bernhard [Langer, captain of the European Ryder Cup squad] picking me.
"Having the three Ryder Cup players at the top is great news for Europe."
Four players share fourth place, four strokes off the lead: Els; 50-year-old Eduardo Romero, who is looking for his third European Masters title; Briton Graeme McDowell, one of Donald's successful Walker Cup team mates; and Australian outsider Craig Spence, the 1999 Australian Masters champion.
Last year, Els was also at 11 under, two shots behind Romero, and he went on to win by six shots in a strong wind.