Lothar M Kirsch, there is a very significant difference between refined and unrefined oils. Refined oils have much higher smoking points. Please click on the link at the bottom of this post and view the chart.
It's also true that in the US canola, sunflower and safflower oils are usually refined. I have seen unrefined versions but they are harder to find. Most olive oils I've seen here are extra virgin so they are unrefined. Sure, refined oils don't have phytochemicals. But, I would rather not have phytochemicals that have my oil reach the smoking point and form toxins. Here is a quote from "Becoming Vegan"
When oils are subject to high temperature cooking (i.e., when they start to smoke), fats--especially unsaturated fatty acids--are damaged and a number of toxic products are formed. These substances can damage the liver, circulatory system, and the kidneys
If there is water in the pan or if the pan is full of items containing water then the temperature tends to be limited and I'm sure extra virgin olive oil would be OK. But as you know before putting any ingredients in the pan people usually get the oil hot first. It could get very hot if the person isn't careful.
Soilman, sorry but I don't agree with most of what you say.
"It's not necessary to use high heat to fry things. I sautee everything (almost) in about a tbsp of olive oil, and never have the heat on High. Whatever you're cooking will cook on med to low heat."
Yeah but people do fry on high heat. I've seen recipes where they tell you to wait until the oil smokes before adding the ingredients. And when I've fried I've seen the oil smoke.
The problem is that no matter how low you put the flame, the oil tends to reach the same high temperature, or very near to it
I don't buy that. When you set the burner higher the oil does get hotter.
Water will not get over 100 degrees C, 212 degrees F -- without evaporating. So anything you cook in a pot of water, won't get any hotter than the water surrounding it.
That's true but we aren't talking about cooking in water. However if you have the pot full of ingredients containg water the temperature will be limited.
Oil will go way over 400 degrees F, 200 degrees C, before it starts burning away
Not true. Here is a list of smoking points for various oils (please click on link below). Oils smoking points range from 225°F to 520°F. Extra virgin olive oil (a type of unrefined olive oil) has a smoking point below 320°F.Smoking Points of Oils