We’ve been buying olive oil all wrong. Here’s what you need to know.

I was drawn in by fancy labels, lower-to-middle price points, and smart terms like ‘cold pressed’ and ‘extra virgin’ — but I never actually knew what I was buying

Auggie Russo puts olive oil on a pizza at his Tiny Pizza Kitchen pop-up in Brooklyn.DESEAN MCCLINTON-HOLLAND/NYT

I’ve been buying olive oil all wrong.

You could say I judged an oil by its bottle. I was drawn in by fancy labels, lower-to-middle price points, and smart terms like “cold pressed” and “extra virgin” — but I never actually knew what I was buying.

That is, until recently when I attended an olive oil tasting at Gift Horse along with Lisa Pollack, an olive oil educational ambassador for Corto Olive Oil, which grows its olives over 80 miles east of San Francisco. I sat in the Providence restaurant with about 15 chefs from Rhode Island and Portland, Maine, where we sampled four oils and I learned just how tricky it is to navigate this $15 billion global industry.

Here are some quick tips to prevent you from carelessly purchasing (and using) any old bottle again.

A farmer at Corto holds olives from their farm in Stockton, Calif.Corto Olive Oil

‘Extra virgin’ is the best. But there’s a catch.

”Extra Virgin” is the highest grade of quality an oil can be awarded. The grades are set by international standards to ensure the oil producers are meeting sensory and chemical benchmarks to be marketed as such. But in the United States, many oils with this highly regarded label — and higher prices — are not required to go through any sort of testing. A 2010 study found that nearly 70 percent of oils labeled as “extra virgin” in American grocery stores did not meet “extra virgin” standards.

”’Extra Virgin’ is basically just a term we see on labels,” said Pollack.

Is ‘extra virgin’ olive oil healthier than others?

While all olive oils contain mono-saturated fats, squalene, and tocopherol, “extra virgin” grade is supposed to have the most healthful phenolics and antioxidants, according to the Robert Mondavi Institute at the University of California, Davis. But it’s not helpful if you don’t know whether your oils have undergone any quality tests.

Olive oil can go bad.

Olive oil is not wine. Meaning, it does not get better with age. Stop saving that “special” bottle in your cabinet. Even the highest quality oils will eventually taste rancid because of oxidation. The bright flavors you may have first tasted within the first six months of those olives being harvested will diminish with time. If you’ve already opened your olive oil, try to use it within three to six months. If you kept it closed, your olive oils should last for up to two years from the harvest date, Pollack said.

How do you properly store olive oil?

While consumers cannot control the age of the oil they buy, they can protect it from its enemies, which are light, heat, and air, Pollack said. You can easily expedite the change from great-tasting to rancid by not storing the bottle properly. So stop keeping it above the stove, or in a clear- or light-colored glass bottle next to the stove or window. Keep your olive oil in a cool, dry location away from any sunlight.

Try to avoid buying olive oils in clear glass bottles, which can increase the chance of rancidity. Oils stored in plastic containers can oxidize faster than those stored in glass or tins. If you do purchase oil in plastic, it should be ok if you use it within three months of opening.

A variety of olive oils.Uncredited/Associated Press

How can I tell if an olive oil is high quality by taste?

“A great olive oil should taste like the fruit that it came from when it was harvested at its peak,” said Pollack, who said premium olive oils will include their harvest date or year on their label.

When you smell your olive oil you should smell the aroma of a garden (greens, herbs, even a whiff of tomato, for instance). When you taste it, it should have a peppery finish (which could initially be delayed as you swallow), and it should leave your mouth feeling clean.

I tasted two versions of the same, commodity oil. The first passed the test. The second was the same oil, but it was oxidized and rancid. Rancid oil, or oils that have been oxidized, can smell like old crayons and taste like rubber or cardboard. It won’t have a peppery finish, and it will coat your mouth with a fatty mouthfeel that will linger unpleasantly.

What brands of olive oil should I buy?

The chefs I spoke to recommended Graza “Sizzle” Extra Virgin Olive Oil, Corto Truly, and Bertolli Rich Taste Extra Virgin Olive Oil — which range from $7 to $24 per bottle. Others recommended heading to your local oil store where you can usually sample various kinds.

If you’re willing to spend a little extra, others said Brightland’s finishing oils are delicious (”The Duo” is $74 for two-375 milliliter bottles).