We usually get great service here, but we came with a friend today who has an allergy to peanuts. How does no one, not even the manager, know whether or not peanut oil is used?

It's usually better to go to the website and call corporate customer service places when enquiring about allergy info than asking at local restaurants. ;)

Arbys does not use peanut oil and there are no peanut products or by products in their foods. Arby removed all trans fat oils in 2007.