Within the last 24 hours MolaKule has posted on this forum that Mobil 1 is comprised of PAO and next generation esters. That's good enough for me and squares with the language found on the Mobil 1 web site about the make up of Mobil 1.
The notion that the base oil in Mobil 1 is nothing but PAO is so far fetched it's ridiculous. The simple truth of the matter is that Mobil 1 has NEVER been a 100% PAO synthetic. Before they used esters and alkylated aromatics for solvency and additive dispersion, they used plain ol' Group I mineral oil. With the advent of the TriSyn formula, Mobil 1 became truly a "100% synthetic" since the mineral oil was no longer used.