A compressor fridge does not have to be particularly level; four degrees should be okay from an operational standpoint.
You would not want to live in an RV that's four degrees out of kilter. That's having one side be about seven inches higher than the other, or the front a couple feet higher or lower than the back. It's more than most people realize, I think.
The main concern with residential fridges is the electric usage if you're dry camping much. If you have electric hookups, that's obviously not an important consideration (and indeed the overall electric energy usage will be less than an absorption fridge running in AC mode).
