Parafin does not equal Wax. The parafin that you buy in the grocery store (wax) is not what is in Pennzoil.

New oils (API SM) are ALL very very good. In the past, synthetic oils would keep your engine much cleaner than regular oils. Today, not so much difference in cleanlinss between regular and synthetic.

The noise will vary with the viscosity of the oil. Generally(not always), lifters like thinner oil. Not all 10W30 oils are the same viscosity. They are within a range of viscosity's. High Mileage oils are generally thicker than regular oils. So, if HM oil made your engine noisier, it is probably because your lifters like thinner oil. You can find out the actual viscosity of an oil on the oil manufacturers web site. Beware, mfg tend to change the blend and viscosity every few years.

Diesel rated oil, (HDMO) is good stuff, but it generally has more additives that can harm your catalytic converter if your engine burns a lot of oil.

20W50 is to thick for these engines unless you have an oil pressure problem.

My 02.