I'm not sure what theory you're talkng about, but all of the oil producers post the certifications, ratings and basic info about their products. The published viscosity for most 5W-30 oils is between 10 and 11 cSt, and for most XW-20 oils it's between 8 and 9 cSt, that's at 212F (100C). That's not a theory it's a fact because each grade has minimum and maximum cSt that the oil has to fall between to receive the grade rating.
UOA's are a lot of fun to read and compare and try to pick apart, but inexpensive ones like Blackstone offers are very limited in determining "wear" in an engine. I'll answer your question with a question, how do you explain all of the "good" UOA's from owners using XW-20 oils in their trucks across all of the brands? And there are people on this site that have reported very high mileage using nothing but 5W-20 during the whole life of the vehicle.
Our patrol Chargers are taken out of service after they reach 200,000 miles and get 5W-20 recycled oil their whole life. I asked one of our mechanics about the cam/lifter issue and he said the last one he sent to a dealership for it was a 2015, he's seen none since model year 2016. That gave me the confidence to buy a RAM and I will use nothing but 5W-20 synthetic in it.
I'm not arguing that using a thicker grade oil in some conditions might be wise, just keep in mind that 5W-30 is also a very thin oil and is only slightly thicker in most cases than XW-20. Depending on how it's formulated a 5W-30 may have a higher viscosity index improver content which makes them more shear prone than a synthetic 5W-20 which will have considerably less or maybe even none. And 0W-20 oils are almost always full synthetic and are made out of the best base stock available to the formulator so they tend to be very, very good oils.
Here is an article written by Doug Hillary, a real expert on oil and UOA interpretation, that fully explains the limitation on used oil analysis.
UOAs are a great tool in the Management of any machinery that uses liquid lubricants. Unfortunately, their real value is often misunderstood by those who contribute to BITOG. Firstly, it is important to realize that you get what you pay for. The most common forms of UOA are limited in their...
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