The original recipe suggested a sunflower oil and that was what I used to take, but nowadays I prefer to use a more neutral tasting canola oil. (whereismyspoon.co)
If you didn't have any avocado oil on hand, you could also use an other kind of neutral tasting oil, or even melted coconut oil. (thehealthyfoodie.com)
To me, avocado has a very neutral taste anyway, which is why I love it so much, since you can flavour it to your liking. (jessicainthekitchen.com)