I use Mobil 1 and have to stay with VW502 oils for powertrain warranty reasons, but does it really matter that most Castrol "synthetics" are actually VERY highly refined dino, plus esters? Yes, it does seem like a truth-in-labeling issue to me, sort of like buying "organic" produce which occasionally gets hit with pesticides from the farm next door, but what is the PRACTICAL implication for one's engine?