For a twin-engine departure (SID) required climb gradient is 3,3. For a contingency procedure (emergency turn, single-engine) req climb gradient is 2,4. Then for a standard missed approach it is 2,5. I have always been taught that if you're single-engine at or below DH/MAP, then you shall follow the contingency procedure. So for instance if you loose an engine below DH/MAP, then following the standard missed approach can get you in trouble.