Do you let your old engine warm up or just get in and drive?

It's not just the engine oil, trans fluid, power steering, gear oil ect. Have you guys ever heard power a steering pump screaming at -20F? I've seen transmission lines come a part at -10F at the add on trans cooler because the fluid was thick and made extra pressure. So if it's below say 10F I let it warm up some. I never throw it in gear and go.