Refining means removing less desirable elements from petroleum until
what’s left is mostly higher-performing molecular structures. Waxy
stuff had to go because it made oil congeal at winter temperatures.
Aromatics had to go because they lost viscosity too rapidly when hot.
Unsaturates had to go because they were vulnerable to heat-driven
gumming and sludging. And so on.
What is 100% true for all the synthetics are uniform sized molecules
that don't exists naturally... so armed with that knowledge you can
shop for the best synthetic price because no matter what brand of
uniform molecules we choose they will meet or exceed our mileage