When buying fries from a fry truck or snack bar, make sure to ask what oil they use in their deep fryer. I’d even suggest asking at restaurants as well; you never know unless you ask.
I recently tried to grab fries at a fry truck and they said they use rendered beef fat in their deep fryer.
I was happy that this snack bar (fries in picture) used canola oil. I needed my vinegar smothered fry fix!