oil oxidation and omega3

I get this question quite often. What oil do you recommend for cooking?
In macrobiotic recipes canola oil, sesame oil and occasionally olive oil are used. Though after my own research I don't use these oils often, except extra virgin olive oil.
When you decide which oil to use for different purposes a few things should be considered

smoke point for an oil varies widely depending on origin and refinement. In general the temperature tends to increase as free fatty acid content decreases and degree of refinement increases.
When oil is exposed to oxidation it becomes rancid and produce free radicals
heating oil also produces free fatty acid and as heating time increases, more free fatty acids are produced, thereby decreasing smoke point. It is one reason not to use the same oil to deep fry more than twice.

For cooking I choose coconut oil, as it is high in saturated oil. Saturated oil is not affected much by oxidation because they are very stable and have a high degree of resistance to oxidation. Keep in mind that coconut oils has relatively low smoking point so it is best not to heat the oil over 177 degrees, unless it is refined.
It is best to avoid oil with high polyunsaturated fat as it is the most unstable fat compare to monounsaturated or saturated fat.

For salads I would use extra-virgin olive oil or flaxseed oil. Flaxseed oil has a nutty taste, rich in Omega3, which is hard to get in my current diet. It is high in ALA which the body can convert to more usable form of Onega 3, EPA and DHA. How much we can convert ALA to EPA and DHA depends on individuals. I recommend plant source of DHA as it is from a renewable source and free from environmental contaminants.
Make sure it is kept in fridge all the time and not use it for cooking.
I freeze my omega3 oils.

There are oils that I would avoid for another reason.
GM oils are a big concern. If your vegetable oils are not organic and do not specifically state that it is not from GM sources, it is most like that it is. Unfortunately there still isn't a obligation for the company to give consumers this fact! Corn, Soy and canola oils are one of the most common GM foods at the moment.