IMO, 48" so I don't have to bend down to use the recep. :wink: Seriously, I don't think a detail area meets the definition in 511.2. If that's true, then there isn't a minimum height.
Please define automotive facility. Is the building, or parts thereof, subject to Article 511 or not, and if so, in what way?
It comes down to, if where the receptacles are to be installed is a classified location below 18", you'd want to put them somewhere entirely above 18", not at 18" or below.