I use olive oil because I like to know where things come from.
Make sure you buy the expensive stuff. I read a book about olive oil called Extra Virginity, and it says most of the cheaper olive oils are adulterated, even most extra virgins sold on supermarket shelves.
does that mean they're sinful? 

In that book some olive oil connoisseur samples some adulterated extra virgin and exclaims, "This is no virgin . . . this is a
whore!"