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I want to know what the difference between olive oil and extra virgin olive oil is. Also, how do you know which olive oil to use in what certain dishes. Last, what is the shelf life of olive oil? Arlene

Here are the various grades of olive oil. If an oil is not graded it should be called virgin or unclassified. The higher the acidity in an oil, the harsher the taste.

Extra virgin olive oil – The most expensive of all olive oils. So to be graded, oil must have perfect flavor and aroma and a color that ranges from light yellow to green. It has less than one percent acidity.

Fine virgin olive oil – With slightly higher acidity (no more than 1.5%), perfect flavor and aroma, and a color ranging from light yellow to green.

Semi-fine virgin olive oil – This is also called virgin olive oil. The flavor, aroma and color (light yellow to green) are acceptable. Maximum acidity is 3%.

Pure olive oil – Or simply olive oil. A blend of extra virgin oil and refined oil. It must have a good flavor and aroma and a color of light yellow. Acidity should be no higher than 1.5%.

Light olive oil – A blend of virgin and refined oils. The word "light" refers to the flavor and color and not to the caloric counts. It has the same number of calories as other olive oils.

Olive pomace oil – Pomace is the portion of the olive that remains after physical and mechanical operations remove the oil and water. Additional oil can be extracted from this pomace using solvents. It is then blended with virgin olive oil and produced at a lower cost than other olive oils.

As a general rule, cook with the pure olive oils and season or drizzle with extra virgin olive oil. That’s because the taste of extra virgin oil may overpower lighter dishes, while you’ll want the flavor to come through in a salad and because heat dissipates the oils flavor. You’ll simply waste fruity oil by cooking with it.

The flavor of olive oil is compatible with herbs and vinegars. It picks up the taste of steamed vegetables, grilled meats and cheeses. It has a relatively high smoke point, which allows you to pan fry or sauté in it without fear of burning. And this makes it suitable for brushing on grilled foods.