Re:Fast Food Oil
I agree with the recommends above. Peanut oil tastes great when well maintained. Separate fryers for fish only. Number of fryers depends on lbs/hour of sales. Look at the fryers, that is one way they are rated. Be prepared to filter daily with a high volume. Also, I'm guessing you're oil will need to be changed out multiple times a week also depending on volume. As has been said, bad oil will ruin your cuisine.
Mmmm, duck fat Fridays at hot dougs! Get ready to wait in line