How can you tell if a natural oil is rancid?

[DigitalRain]

I have bottle of Now Jojoba oil that I have had at least 2 years. I dug it up today. Its smells fine, but it has a thick darker colored residue at the bottom. I shook it up and the residue dissolved back into the oil. Is it rancid?

 

[PrincessM]

I know that I have to keep coconut oil in the fridge because it's shelf life is not long outside of the fridge. It starts getting this funny smell if left out, especially if it's in a liquid state.

 

[Chimma]

I thought jojoba oil never went rancid. Here's the EPA's site on jojoba oil: http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_067200.htm