Some oils damp noise better than other oils. It has nothing to do with the oils quality, i. e. the oil's protection of the engine. Try a different brand of oil next time you do an oil change.
There is always a lot of discussion about the oil viscosity. First, the "W" winter viscosity is measured at very low temperatures...-35°C for 0W, -30°C for 5W, -25°C for 10 W. These are all part of the SAE J300 spec. The other viscosity number is measured at 100°C. It is important to match the viscosity of the oil to the temperatures actually inside the engine at the bearings, not the water temperature. In very hot weather, especially if the car is driven hard, it might be prudent to go up to 30 wt. The film strength of the oil, other things remaining equal, relates to the viscosity of the oil. If the bearings are of adequate size, then lighter oil is fine--the load on the bearing is spread over a large enough surface area so the the force is spread and the oil film remains intact. Keep in mind that a 747 jet engine uses oil of about 5 wt. Kia warrantees our engines for 100,000 miles if you use a 5W-20 oil and change it on schedule. I'm just guessing that they know more about the engines than we do.... Even a very large diesel engine putting out 7,500 hp per cylinder only uses a 30 wt crankcase oil. In general the viscosity used won't make any difference. I wouldn't use 10W-30 in a northern Canadian winter, and I'd be loathe to use a 5W-20 in the hottest parts of Oz or Death Valley. Caltex is a Chevron brand and good stuff.
Blend, schmlend. Some synthetic base oil can be mixed into the conventional base oil for a couple of reasons. Really cheap conventional oil can be used and add some cheap so-called syn, the whole mixture now comes up to spec, and it can be marketed as something special...synthetic blend oil. Or, a top syn can be mixed with a top conventional oil to improve the mixture and make an excellent oil. Yes, there are synthetic oils of varying qualities. Some are little better than the best conventional oil and not worth any extra price.