The generator has a feature that auto-controls the engine speed based upon the electrical demand. This feature can save a ton of fuel AND can keep the noise level down. Make sure your generator has that feature.
DO NOT - I repeat DO NOT use engine auto-controls with a modern "energy saving" refrigerator.
I learned a $1,460 lesson in the hurricane Irene blackout. My relatively young refrigerator automatically enters a "low energy" mode that draws just enough to keep things cool (especially overnight when the door isn't opening and closing) and that "just enough" isn't quite enough to pull the generator out of "resting" mode - which means that the generator is putting out about 55 volts, at a lower than normal frequency (about 35 hz) and this killed my fridge motor. It didn't happen all at once, and the power was back on before we noticed that things were melting.