Denny, I checked those links you sent. The Valvoline site is down for repairs and the rest are advertizing copy put out by the oil companies promoting their most expensive motor oil products.
That hardly qualifies as "unbiased" product reviews.
From what I have read in unbiased reviews, I would liken synthetic oil to plasma coated moly piston rings or gapless piston rings. Those rings are an advantage in race engines according to reputable race engine component suppliers like Sumnmit Racing Equipment. Those same suppliers have told me that plasma coated moly rings and gapless rings offer no benefit in a daily driver or even in a high performance street engine. In other words, except in a race engine the unbiased experts call plasma coated moly rings overkill and a waste of money.
One engine building "frill" that is now universally recommended is cylinder wall honing with a torque plate.
