With the win, the A's moved into a 6 1/2-game lead over the Angels, who lost to the Mariners on Monday, and have won 13 of their past 17 games.
Loaiza has not only been the best pitcher in the A's dugout during this month, but he has arguably been the best pitcher in the Majors with a 1.48 ERA and four wins.
"Thought E-Lo was excellent again," said A's manager Ken Macha. "He's had four great starts in a row."
Loaiza improved to 30-18 for his career during August, and he was very efficient against the Red Sox with one walk and four strikeouts in 111 pitches -- 77 for strikes. In his past three starts, the righty has 18 strikeouts and one walk. Loaiza hasn't given up an earned run in 28 2/3 innings.
"He's been a command pitcher, and now he has command with both sides of the plate with his cut fastball," Macha said. "The ball is jumping out of his hand right now. He elevates his fastball on occasion and he can hit 92 and 93 [mph] with his fastball."
Loaiza scattered five hits against Boston and faced a threat in the third inning when the Red Sox loaded the bases with two out after Mark Loretta was hit by a pitch. But the right-hander reached back for his fastball and got the punchout to end the inning against a swinging Kevin Youkilis.
"This team makes you work for every out that you get, and [Loaiza] was equal to the challenge," Macha said.
The 34-year-old maintained consistency on the mound even while having long breaks in the third and fourth innings when the A's sent 16 batters to the plate in the two innings.
In the top of the fourth, Loaiza had enough time to watch an episode of "Entourage" on the bench, while the A's had four hits and three runs in the inning. But Loaiza didn't let the 60-degree night get to him as he wasted Boston's next three hitters with nine pitches in three minutes.
Loaiza seemed to steam through the Red Sox lineup that was without Manny Ramirez and David Ortiz, but the A's did have a hiccup in the field from first baseman Nick Swisher and shortstop Marco Scutaro.
In the bottom of the fourth with two out and a runner on first, Carlos Pena hit a grounder to Swisher. Instead of the 25-year-old stepping on his base to end the inning, he threw to second base as if he was starting a double play. Not only did Scutaro make a nice grab as he was about five feet from the bag, but he threw back to first for the "fourth" out of the inning after stepping on second. Even first-base umpire Paul Schreiber called the out at first base.
Loaiza wasn't amused by the play at first because he thought that Swisher's throw could have ended up in the outfield, but laughed about the "fourth" out after the game.
"I was like, 'What's going on,'" Loaiza said. "I said to [Swisher] 'From now on I'm going to tell you how many outs there are in the game.'
"If Scutaro wasn't there, who knows what would of happened? They turned two with two outs; it was kind of funny."
Swisher said he didn't realize what he had done until "Loaiza stared a hole through [me]."
"That was awesome," Swisher cracked. "The funny thing was that Scutaro threw it back to me. [Third-base coach Ron] Washington talked to me on the bench and said, 'Don't you know you can just touch first?'"
While Swisher smiled in the field, he and Frank Thomas each hit their 28th homers of the season in the seventh inning off Keith Foulke.
It was Swisher's 51st of his career, and for Thomas it was his 476th. That moved Thomas into 23rd place on the all-time list, passing Hall of Famers Willie Stargell and Stan Musial.
"[Thomas is] just putting himself up with the great players," said Macha, who played with Stargell with the Pirates. "The frightening thing is that he is in such good shape.
"Some of the balls that he has hit this year have been way out. A lot of guys get to that age and they can't get to the good fastball; he's still doing that."
Bobby Kielty and Jay Payton also combined for four hits and four RBIs for the A's offense. Adam Melhuse pinch-hit for Thomas in the eighth inning and nailed a two-run homer off Foulke. It was the first pinch-hit homer for the A's since Scott Hatteberg on July 21, 2004 at Seattle.