while this may be true that oils are now labled syntetic and synthetic blends (agreeing that MOST are synthetic BLEND), saying there is NO problem with doing a straight conversion is a bold statement. That statement would lead one to beleive that synthetic is synthetic... which it is not. Oils like royal purple and especially other lower quality oils over time may actually clog or partially clog/build up in oil filters or oil lines and the remainder normally settles in the bottom of the oil pan. That is a big part of the reason you prepare your engine for the swap.
Also the problem with alot of other "full synthetic oils" and "synthetic blends" is that the legal classification for synthetic oil is an oil that meets X standards for purity, so legally they can brand their really clean oil as synthetic because it meets the standard, but it can still come from the ground, not a lab. Did you know that?
Plus! oil isnt the only factor in protection and how clean it stays, your filter plays a huge role, Amsoil Ea filters have a filtering efficiency of nearly 100%, i think the actual number is around 97% at 15 microns(using a bypass system will bring that number down to around 5), I challenge you to find a better filter, you will be lucky to find one over 80%, Most are around 50%.
But remember, cleanliness also is not the ONLY factor, an independant testing facility ran tests that showed Royal Purple showing a significantly high volatility rate with a 12.51% boil off rate. This compares to the Amsoil with only a 4.47% volatility rating. Wear scars were also smaller with the amsoil.
I pay $58.25 for 6quarts of Amsoil and an Ea filter, and I usually make it 15,000-20,000 miles in that 1yr period before I have to change, and truthfully I could probably go another 5,000 miles, I just change it at the interval for the principal fact thats what they recommend.