Why should I use olive oil?

According to Harold McGee, using olive oil to fry is basically a waste of money. "After I’d heated them, none of the olive oils had much olive flavor left. In fact, they didn’t taste much different from the seed oils."

According to a Spanish study I have access to, you could use high oleic sunflower oil for frying as it degrades better.

Olive oil is preferred for the flavor it imparts, and by many because it is healthier than other oils. As far as frying goes, it is actually not that great since it has a relatively low smoke point, meaning it will start smoking on you at a lower temperature.

First at all I apologize for my English.

Basically remarks made before are not really true. Smoke point took alone does not mean anything. There are other consideration that must be done to analize oil transformation.

• What is friying?

Let's go in order considering two aspects: oxidation parameters and healthy parameters:

Frying is an accelerated process of oxidizing (air oxigene attacks lipidic substratum).
The transformation is more accelerated as higher is the oil unsaturation (presence of double connection that is a point of weakness).

So the stability of fatty acids is related to double connections in its structure and decreases in the order of those categories:

-saturated: 0 unsaturation
-monounsaturated: 1 unsaturation
-poliunsaturated: 2-3 unsaturations

So it means 0 unsaturation are definitely more stable oils during frying.
But there's an healthy parameters to be considered: saturated fatty acid are hamful for cardiovascular illnesses.

satured: lard, palm;
monounsaturated: olive, sunflower (high oleic acid);
poliunsaturated: maize, soy, sunflower (high linoleic acid);

So until now the better choice are monosaturated oils!

• The thorny subject of smoke point:

Often associated to formation of acrolein, is closely related to the physic state of oil and not to its fatty acid composition.

The presence of humidity and acidity (free fatty acid), decreases the smoke point.
So for the same acidic composition smoke point descrease for oil with more acidity.

• So which is the better oil to fry?

Although smoke point is lowest you have to consider the oxidation stability as well.
Even if you can see an oil smoking it does not always mean that the oil decomposes.

That's because they wrongly talk about smoke point as the central point instead of a more complex process called pyrolysis that is:

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxidizing agent (normally oxigen).

So here we came!
Even if extra virgen oil has a less smoke point is the more oxidation stable oil thanks to its liposoluble antioxidant (Vitamin E) and idro-soluble (biofenoli).

I hope to have explained in better way why the smoke point is not the right (or better the only one) property of oil that has to be considered.

• About the taste:

Of course the extra virgen oil has a strong taste and it's used for food without own taste as said potatoes, fries.
To not alter some taste food (fish) can be used for example peanut oil that does not have a strong taste (for its good combination of oxidation parameters and smoke point).

Other staffs should be considered.

• Not use the same oil to fry? it's true, but there is something called polar compound formed during frying that is the health indication of frying oil.
  That means that should not exceed a limit value (defined by healty department; some place the value is 25g/100g, but that means pretty more than 8 home frying; it is to control restaurant industry).
• heat the oil before but not cross 180ºC / 356ºF
• do not bathe cold food even if the box says yes
• try to keep the temperature constant
• do not salt/sweeten during frying but after it
• fry little portion of food to shorten the fry time

I hope I've been helpful!

Kind regards!

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• Editing to answer to comments:

@Aaronut I completaly agree with you. I always advice to not believe surfer doctor improvisation. This is just a place for opinions!
I agree that you need reliable source! I'm gonna give you some!
But first of all I want to say. Don't trust on everything because market business let say many deceitful things! Market business is misleading! It's able to corrupt everything.

I'm just pretty surprise of your doubt: "saturated fatty acid are hamful for cardiovascular illnesses"
Satured fatty acid are responsible for cholesterol. Cholesterol is responsible of coronary disease.
Do you agree with me about it?
Anyway if you think this is my opinion...
here you some reliable sources! (All are Government Institutes! No privates or indipendents!)

• CNR: The Italian National Research Council (last pages in english)
• INRAN, Istituto Nazionale di Ricerca per gli Alimenti e la Nutrizione.
• Italian Department of Health law.
• Federico II University Ph.D. (page 6)

I'm sorry but I don't have time to find more!
By the way I want to show all theory :) There is an opposite one.
But in my opinion a single researcher can be corrupted very easy. He's Ronald Krauss and I don't really have time to find his study.

@rumtscho I definitely prefear Extra Virgen Olive oil. For some frying (very few) I use Peanut oil to not alter some food taste.
I will answer to other comments as soon as I can.

Kind regards to everyone!

I think the best thing to do is use olive oil for cases when you are drizzling it on or cooking for a short time. Otherwise, use vegetable/canola/etc.