Originally Posted by FordCapriDriver
Some synthetic base stocks like PAO if i remember correctly have intrinsic solvent characteristics, others like Group III and Esters not so much.
You've got that somewhat backwards.
As the purity of the base oil increases with respect to catalyst derived and solvent dewaxed bases, the solvency and polarity decrease. So, Group I is the most polar of the traditional hydrocarbon bases and as you go up the chain, this decreases until you are at Group III where you have next to no solubility, which is only eclipsed by PAO, which is even worse. These bases offer better thermal stability and superior cold temperature performance (particularly PAO) but because they are so pure; so "neutral" they that an oil blended with them be dosed with something else to improve solubility. This is either a lower group base or something like POE. Esters have a great deal of polarity, which is one of the reasons Mobil uses them in their PAO-based formulations and even shows them in their blending guide, as they facilitate proper solution of the addpack and give the oil the ability to better keep contaminants and combustion byproducts in solution.
GTL, being a Group III product, would be as bad as VISOM and other group III bases, if not worse, in terms of solubility and is probably as close as you can get to PAO in that department.