Since Olive Oil has a smoke point of only 320 degrees Fahrenheit it makes the Olive Oil not very good for use in a deep fryer to fry foods.
However you can fry the foods in a deep fryer with olive oil if you want too and I have done so myself but I find that olive oil doesn't work very good for deep frying foods.
I prefer to use Canola Oil or regular vegetable oil to cook foods in a deep fryer or even peanut oil which is what most food establishments use to cook foods in their deep fryer.
If you buy fast food and you have fried onion rings or fries then it's very likely that the foods were deep fried in a deep fryer using peanut oil.
Peanut Oil has a very good smoke point which makes it one of the best cooking oils for deep frying foods.