I sometimes put olive oil on my hair for a few hours before washing, as a conditioning treatment. Not long ago, I was doing this and Samantha showed a massive amount of interest in the oil. She was positively excited..
After googling and failing to find anything wrong with olive oil and cats, I gave her a little. She loves it.
She's very prone to furballs and constipation, but Katalax is expensive and lactulose seems related to cystitis (by drawing fluids to her bowel). I often forget to buy other furball treatment and never have it in when needed.
Just thought I'd pass this on.