OAKLAND, Calif. - Adam Melhuse was just the latest member of the surging Athletics to have himself a big game.

Melhuse contributed a grand slam and five RBI to Oakland's record-setting offensive output and Mark Kotsay went 4-for-4 to lead the Athletics to a 13-3 win over Pittsburgh Sunday for a three-game sweep.

"Earlier in the year, runs were hard to come by and we were relying on our pitching," Melhuse said. "Now it seems like we're all clicking. When guys are getting all those hits you want one yourself. It makes you focus in a little more."

The Athletics have scored a major-league leading 95 runs in June, including 79 in the past seven games. The A's have also set an Oakland record with 104 hits in that span.

"This is one hot ballclub," said Pirates manager Lloyd McClendon. "They beat us up pretty good. We scored a lot of runs but we're not getting anywhere."

Scott Hatteberg homered and drove in three runs, extending his career-best hitting streak to 14 games. Oakland has won eight straight, its longest winning streak since last Aug. 23 to Sept. 2, and 11 of its last 12 to surge into the AL West lead.

Oakland has won 10 of 11 games without star third baseman Eric Chavez, out with a broken bone in his right hand.

Eric Byrnes hit his third homer in two days and drove in three runs as the A's maintained the best record (81-47) in interleague play, including an 18-0 mark against the NL Central.

Jermaine Dye and Erubiel Durazo also had three hits each for Oakland.

Pittsburgh has an ERA of 8.32 (61 runs in 66 innings) during the losing streak.

Oakland, which had 18 hits, has scored 10 or more runs in five of its last six games, and has 14 homers in that span. The A's won 11 games on a homestand for the first time since 1959 - when they were based in Kansas City.

"I don't think I've seen anything quite like it," Pirates starter Kip Wells said. "They get two guys on and suddenly they have a big inning."

Craig Wilson and Daryle Ward homered for the Pirates, who have lost 13 of 14, dropping eight straight for the first time since losing nine straight Sept. 9-17, 2000.

"We're on such a bad streak we just need to get away from here," said outfielder Rob Mackowiak, who left with a bruised left shoulder in the fourth. "We haven't done anything well on this road trip."