WHAT’S the best oil for everyday frying? Some markets where I shop offer more than a dozen oils, from argan and avocado to tea seed and walnut. I’d long figured that the choice is a matter of taste and price. I usually use canola oil because it’s neutral in flavor, a good source of omega-3s and inexpensive. Like soy oil, it costs about a dime a tablespoon, whereas extra-virgin olive oils can run well over a dollar.

Partisans of the olive maintain that a high-quality extra-virgin oil brings its special flavor and health benefits to foods cooked in it. More recipes now suggest it for frying and other high-heat techniques, not just for last-minute drizzling. But does it make enough difference that it’s worth a tenfold premium in price?

I investigated the flavor question by heating 15 oils — 4 olive and 11 seed oils — with nothing else in the pan, so I could taste what heat alone does to them. And I served some of them to trained oil judges.

We were surprised at how thoroughly heat obliterated the flavors in cooking oil until they all tasted more or less the same. Even prize-winning, and costly, extra-virgin olive oils lost much of what makes them special, though they retain their apparently healthful pungency. To get food with the green and fruity flavor of good olive oil, it seems more economical and effective to fry with an inexpensive refined oil and drizzle on a little fresh olive oil after cooking.