I read an article about 5 years ago on a hot rod car magazine site where one of their "experts"had written an article on synthetics vs dino. They had done lab testing on numerous brands for both conventional and synthetic. Biggest difference was cold weather starting, heat dissapation, and life span of the oil. One interesting thing they noted was that when they took the engines apart after testing, the synthetic motors had bronzed pistons and sleeves. They figured the oil worked itself into the metal. They then ran the engines with no oil. I don't remember the exact numbers, but the synthetic motors ran quite a long time without oil.
They also said that synthetics should give the appearance of burning oil. The reason is that they have an additive (up to 20% in some brands) the prolong the life of the oil and that the additive burns off.
At the end, the number one rated oil was Mobil 1 followed by............Walmart supertech synthetic!!!!!! (I wonder who makes the oil for Walmart)
The writer said he uses supertech in all of his motors except his 72 mustang which he put Mobil 1 in. From what I gathered, his point for the most part was that all synthetics are good and a few are a little bit better.