NEW YORK (CBS 2) — According to a recent study, the olive oil you use for cooking may not be what you think it is.

A lawsuit filed by chefs and restaurants claims that several prominent companies have been combining their olive oil with cheaper oils – but still branding it and selling it as high quality, extra-virgin oil, reports CBS 2’s Mark Morgan.

Among the specific brands named in the suit are Filippo Berio, Bertolli, Mazola and Rachael Ray.

“It’s not right,” said Luz Vasquez, Queens resident. “It’s supposed to be pure. If it’s not, we’ll have to pay a little less.”

Others agreed.

“It’s fraud,” said Manhattan resident Jennifer DeSimone. “They can’t do that, I’d be very upset if I was deceived like that.”

Several top retail stores, including K-Mart, Wal-Mart and Target are specifically named in the lawsuit and accused of selling the compromised oil.

The suit is based on a study released last month by the Olive Oil Center at the Univ. of California at Davis. The report found that 10 percent of olive oil made in California and 69 percent of imported olive oil fails to meet standards set by the Dept. of Agriculture.

The survey has drawn criticism, due to its small sample size and random selection: 19 brands were purchased from retailers in San Francism, Sacramentio and Los Angeles.

Not only is “extra virgin” more expensive, nutritionally there is a difference as well, and helps make it the choice of many consumers.

“Extra virgin and virgin olive oil are the least processed,” said diet expert Elisa Zied. “That means they have the most antioxidants, and they’re specifically called polyphenal antioxidants – these are very, very heart healthy.”

The plaintiffs in the suit are seeking an injunction to force the manufacturers to stop distributing what they feel is a fraudulent product.

In October, the U.S. Department of Agriculture is expected to implement new standards to eliminate concerns about the accuracy of those labels.

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