here's a brief explanation i found which might clear things up,
"Using 10W-30 as an example, we can determine that at an oil temperature of 0 degrees , the oil has the properties of 10 weight motor oil while at an oil temperature of 100 degrees, the oil has the properties of 30 weight motor oil"
I personally use "Havoline Synthetic Blend" 10W-40, engine has never been quieter and feels solid, even after 150,000ks. You said that it is noisy when hot, so a 10w-40 would be better than a 10w-30 in your case. So when you take into account our worn engines and high temps in oz, especially coming into summer, 10W-40or50or60 should be fine.
another quote:
"As mileage adds up and internal engine wear increases bearing clearances, it may be wise to switch to a slightly higher viscosity rating to prolong engine life, reduce noise and oil consumption. For example, if an engine originally factory-filled with 5W-30 now has 90,000 miles on it, switching to a 10W-30 oil may provide better lubrication and protection. The thicker oil will maintain the strength of the oil film in the bearings better so the engine will have more oil pressure. This will also reduce engine noise and reduced bearing fatigue (which can lead to bearing failure in high mileage engines)."