* Q2 EPS C$0.21 vs. C$0.71
* CFPS C$0.51 vs C$1.12
* Maintenance, lower prices pressure results
CALGARY, Alberta, July 27 (Reuters) - Second-quarter profit at Canadian Oil Sands Ltd, which owns the largest stake in Syncrude Canada Ltd, sank 71 percent due major plant maintenance that reduced production, lower oil prices and higher operating costs.
Canadian Oil Sands, which has a 37 percent stake in the massive Syncrude tar sands mining and synthetic crude operation in northern Alberta, earned C$101 million ($101 million), or 21 Canadian cents a share, down from a year-earlier C$346 million, or 71 Canadian cents a share.
The result lagged an average estimate from analysts of 32 Canadian cents a share, according to Thomson Reuters I/B/E/S.
Cash flow, a glimpse into the company's ability to fund development and pay out dividends, fell 55 percent to C$245 million, or 51 Canadian cents a share, from C$544 million, or C$1.12 a share.
Canadian Oil Sands said the results were hampered by maintenance outages at one of its coker units and at a vacuum distillation unit, both parts of Syncrude's upgrading plant. The facility turns tar-like crude from the oil sands into refinery-ready light oil.
During the quarter, sales averaged 90,000 barrels a day net to the company, down 13 percent from a year earlier, due to the outages.
The company realized C$90.45 a barrel for its crude, compared with C$111 a barrel in the second quarter of 2011.
Operating costs averaged C$50.66 a barrel, compared with C$37.07, reflecting to lower production and higher maintenance expenses, the company said.
Canadian Oil Sands also said it reduced planned capital spending by C$95 million this year to C$1.12 billion, though it does not expect any changes to costs or completion dates for projects.
Canadian Oil Sands shares closed down 14 Canadian cents at C$21 on the Toronto Stock Exchange on Friday, down about 20 percent in the past year.