I always use the lowest temperature that I can input. But GPT-5 doesn't support a temperature setting. You'll get something like:

{ "error": { "message": "Unsupported value: 'temperature' does not support 0.0 with this model. Only the default (1) value is supported.", "type": "invalid_request_error", "param": "temperature", "code": "unsupported_value" } }