RE: What to fry your fries in...
in most of the uk, beef tallow (they call it beef dripping) is still used at almost every chip shop in every town, not just for fries but for everything deep-fried, including spam..
when i was a kid, i noticed at the local fairs that the grills they cooked the burgers on drained directly into the fryers for the fries. those were the days....:)
to answer your question though, yes, it does make very crispy and tasty fries but, they are plenty greasy.. much greasier than fries cooked in peanut oil.