Many olive oils have been mixed with peanut oil, soy and lampante (lamp oil,rotten olives) to save costs.
Companies that refine rotten olive oil give you a tasteless and odorless product. Companies will have legal frauds (extra light olive oil). extra light olive oil has the same amount of calories just the goodness refined out of it. This legal in the states except for Europa. Rancid olive oil has free radicals and peroxides in it. Below is a cheat sheet to follow when looking to purchase healthy olive oil.
OLIVE OIL CHEAT SHEET
Taste it first: Keep in mind that good oil has an intense flavor profile that will likely burn the back of your throat a little bit: It should be fruity, peppery, and even bitter.
Don’t buy in bulk: Buy straight from purveyors; avoid middlemen. Go for smaller quantities that you can consume relatively quickly.
Compare bottles: Choose oil bottled in stainless steel. If not possible, darker bottles do a better job of protecting the oil from light.
Be wary of meaningless labels: Light, pure, refined, virgin, first-press (EVOO has to be first-press, by default), cold-press (most oils are made with centrifuges, not presses—and all purveyors process the oil in cold) are all marketing plays devoid of meaning.
Check the date and place: Olive oil is olive juice—olives are a fruit and are perishable. The taste of the oil begins to deteriorate quickly, as soon as the olives are milled. There should always be a best by, or bottled date. Best by dates usually expire two years after the olive oil has been bottled. Also see where it was made, as packed or labeled in Italy, does not mean that it was, in fact, made there. Look for the specific mill—or PDO (protected destination of origin) or PGI (protected geographical indication)—which are protected “Made in Italy” seals.