American Luke Guthrie extended his lead to four shots at the halfway stage of the BMW Masters as former world number ones Rory McIlroy and Lee Westwood struggled to make an impact in cool and windy conditions in Shanghaion Friday.

The 23-year-old American offset five birdies with four bogeys in his one-under-par round of 71 at the Lake Malaren Golf Club for an eight-under total at the 77-player no-cut European Tour event.

"Anything in the reds today was a good score. The winds were back up and it was a little cooler, I forgot my sweater and I was a little cold out there today," Guthrie, who led by three shots after the first round, told the European Tour.

"I played solid again and made a few more bogeys which was disappointing, kind of hit a few poor shots but hung in there and posted something in the red.

"Its only halfway, there is so much more golf to go. Will have to see what the weather does, I think it is meant to get a little better."

England's Simon Dyson had a disappointing double-bogey six on the last to sign for another 70 and fall into a six-way tie for second alongside fellow Britons Craig Lee (70), Paul Casey (70), Scott Jamieson (68), Thailand's Thongchai Jaidee (70) and Ricardo Gonzalez (67) of Argentina.

Lee's round was boosted by an eagle two on the 16th when he holed out from the middle of the fairway.

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The Scot had collected his putter from his bag before the roar from the gallery told him it was not needed as the ball bounced past the hole and rolled back down the slope and into the cup.

"Just when I was starting to get a bit frustrated about not moving forward, then bang. I hole a four iron straight into the wind from 188 yards," Lee said.

"Always helps the scorecard, especially from a birdie on the hole before, so it was great."

Gonzalez, who celebrated his 44th birthday on Thursday, produced the best round of the day and it could have been one better if not for his only bogey of the day on the last.

John Daly is another one of the over 40s club trying to claim victory at the $7 million event, the first of four in the European Tour's Finals Series to determine the order of merit winner.

The big hitting American fell back into a tie for ninth with Spain's Gonzalo Fernandez-Castano (71) at two-under after two bogeys and a double in his final five holes resulted in a 74.

That was still one better than McIlroy (72) and Westwood (71), who are tied for 12th at one-under for the championship.

Race to Dubai leader Henrik Stenson was further back on two over after a 74, two shots adrift of his nearest challenger in the money list race, Graeme McDowell(74) of Northern Ireland.