i just swapped to 20/50 yesterday because i have oil pressure problems at 160,000miles with no rebuild. drove it and pressure is fine now. but i live in the Seattle so it never snows here just rains, so no real cold probs.
wazazzle - just upping the viscosity may help the pressure, but you're gonna be volume deficient. If the clearances are loose enough because of wear/tear to cause a drop in pressure -- that's a sign that it's time to fix the illness rather than treat the symptom. Time for a rebuild my friend. The heavier oil simply masks the symptom -- it doesn't fix the problem. Running higher viscosity oil for low oil pressure is the equivalent of putting a blindfold on when you discover you have gangrene in your foot. You won't see it -- but you're still have a problem that's only gonna get worse and will eventually keep you from going anywhere.