I'm by no means a chemist or anything, but I know that some brands definitely do not use VG/PG or at least use little enough that they can claim not to. As far as the thickness of the juice -the pens I have, i wouldn't even consider it to be juice. Its very non-viscous oil. I can put it upside down and it takes 20 minutes for the oil to flow to the bottom of the vial so I'm pretty sure it hasn't been thinned, at least not in any meaningful way. The pens do get clogged with oil sometimes and you just have to let it heat up really hot and take a massive hit to clear it out.