You can really use any cooking oil to fry latkes. However, while it’s a little indulgent, I like to cook the pancakes in mostly olive oil (pure, not extra virgin), with a tiny bit of butter added in for flavor (which is NOT kosher, so don't do that if you are keeping kosher). You can also use just olive oil, or vegetable, canola, or grapeseed oil. And do not whip out the fancy bottle of extra-virgin olive oil for this purpose. You will want to save that for your vinaigrettes and glug in the less expensive pure olive oil when you are frying.