[shvcko99]

When two cooking oils of different brands or compositions are mixed and heated together, could they react and produce unfavorable (i.e. unhealthy, carcinogenic or toxic) compounds? Is there any study or news on this issue?

[Corribus]

Not really clear what you're after. Cooking oils are all mixtures (of triglycerides). If you mix two cooking oils, you get a mixture of mixtures, both of them having many of the same lipids. The lipid profile will be different, but they are all lipids. Your flavor might be different, but they are basically the same class of chemicals.

[Babcock_Hall]

I have not looked into this, but I cannot come up with a reason why this should happen.

[shvcko99]

Not really clear what you're after. Cooking oils are all mixtures (of triglycerides). If you mix two cooking oils, you get a mixture of mixtures, both of them having many of the same lipids. The lipid profile will be different, but they are all lipids. Your flavor might be different, but they are basically the same class of chemicals.

but in addition to the main ingredient, could different oils contain different addictive or other chemicals which may react together

[Borek]

No sane chemist will tell you it is impossible.

But: it is also possible to be hit by a meteorite, yet nobody cares.

[jeffmoonchop]

A lot of cooking processes involving burnt fat or seared meat involve the production of carcinogenic substances. But they just taste too good for most people to care. Don't burn your food then eat it and you'll be fine.