In reading the thread about canola oil (which I don't generally use)a question occured to me.
I know this is perhaps niave...
I don't cook often with oil. I use EVOO for salads, peanut oil for stir fries, keep a bottle of sesame oil in the fridge. I buy bottles that I will use within a few months. I have never encountered a rancid oil as far as I know. I once had a bottle of almond massage oil that eventually smelled kind of old, so I tossed it.
How do you know when it's rancid? How does the smell change? Does it change color?