If flying against no one, you can lightly configure a 762 to make a small profit (Standard Y, Prem C)
But if your going to run all Prem C and Y, chances are you wont make enough to cover overhead. It may show a profit, but factor in overhead and you'll be operating at a loss. Keep your total seats above 180 is my recommendation.
767 family has tough operating economics (except for 764). Use them wisely.