Its all about the main and rod bearing clearances and the pressure/volume ratio of the oil pump.
When you rebuild an engine for racing you use the tightest clearances, and run a 0w10 for qualifying. (Faster) then switch to a "heavier" oil for the race.(Better durability) Joe Gibbs Racing sells a bunch of special synthetics some with extra zinc for breaking engines in, some that are for higher RPM's, etc. Good page to look around at...
Typically you want a high pressure NOT a high volume pump because the pressure on the oil is what keeps the clearances where they should be. A high volume pump usually will cause over-oiling to the top end and cause leaks at the valve cover gaskets.
Just a couple opinions... Probably worth what ya paid for em...
Dave