I use regular old QS 10w30.
One thing to watch for is Viscosity Modifiers in oil. It's quite common, and I'm sure they are probobly in the oil you just used. Viscosity modifiers (VM`s) are long chain polymers that are added to a light base oil to prevent it from thinning excessively as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as the 'X'W number indicates. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. Unfortunately, VM's will shear over time, reducing their effectiveness, and can burn and form deposits that cause ring sticking. Most manufacturers have shied away from oils with more than a 30 point viscosity spread. Notice how hard it is to find 10W-40 anymore? For awhile, GM threatened to void warranties if 10W-40 was used.
AMSOIL uses no VM's in their 10W-30 and 15W-40 weights, and Mobil 1 formulates their 5W-30 and 10W-30 without VM's. Oils that start out with heavier base stocks, such as 15W-50 and 20W-50 need very small amounts of VM's, however, I can't recommend either of these 2 oils if your wintertime temperatures go below 30 deg. F. A heavy weight like that will be slow to circulate and could cause bearing damage.
Low oil pressure though may be a sign of worn bearings in the bottom end...does it drop when the oil temp rises? Or is it always low?