So you’ve just mastered identifying the subtle differences between a malbec and a merlot, good for you. Now you get to graduate to oil tasting – important stuff unless you want some processed imposter dressing your salad. Gerrie Duvenage, head oil maker at Morgenster (arguably home to the best oil in the country), suggests the following as a guide to buying the best:
Make sure it’s in a dark bottle, there aren’t preservatives in the good olive oils so they are sensitive to sunlight. Extra Virgin olive oil is completely unrefined and natural and embodies the health benefits that are so widely punted.

Morgenster truffle oil
Warm some oil up between your fingers and sniff it – if it smells like old bacon fat, it’s rancid and of poor quality. Neither should it smell mouldy or muddy.
It should not smell like wine – that means something went wrong in the oil-making process and your oil will taste like vinegar.
“It needs to smell like freshly cut grass or fresh green fruit like apples,” says Duvenage. “Don’t be put off by a bitter, peppery taste, it’s a sign of a good olive oil,” he says.
According to Duvenage there are three types of olive oil: delicate which has a sweet taste and is ideally suited for salads and fish. Then there are medium and intense types – these taste peppery and bitter and are best suited for red meat and soups.
“Look for the SA olive seal on olive oil bottles, so that you know you’re buying quality olive oil and not the cheap imitations that are being dumped on our market,” he says. If it’s imported and costs less than R100, chances are it’s not the real deal and not very healthy.

Most important feature is freshness, therefore try to figure when was it bottled. Check “Best before” and “Lot No.” (It frequently discloses bottling date after the “L” printed on the back label or on the bottle). I do not buy anything older than 12 months!
So much more we need to know about this:
Cooking with olive oil is not good, because oil should not be heated.
Cold pressed against UHT (heated) oil.
Mixed oils usually contain oils that are bad for you.
Please may we have the complete truth about oils and mono-unsaturates.
Olive oil is excellent for cooking Mo! Also, when frying, it stands for higher temperatures than the average frying oils. I agree EVOO is more expensive and in your market it may not be a wise solution.
http://health.clevelandclinic.org/2012/05/heart-healthy-cooking-oils-101/