I have a 2005 Pontiac Grand Prix GXP with 128,000 miles. At cold idle, the oil pressure drops to 3.5-4 PSI and the engine has a tapping noise. After the engine has warmed to normal operating temperature, the oil pressure is 12 PSI at idle. At cruising speed, oil pressure is 50 PSI. GM recommends 5w-30 oil. Would I benefit switching to 0w-30 which would make the oil easier to pump when the engine is cold? I've also read of using a heavier weight oil to increase oil pressure, but understand while it may increase pressure it won't get oil to the necessary parts of the engine to stop the tapping.