Vegetable glycerin (VG) is much more viscous than PG and, consequently, it's got a harder time soaking in the wicks. That is a non-situation for many sub-ohm tanks which have large wicking holes but might be a problem for tanks that happen to be possibly a bit older or not intended for sub-ohm vaping.Supplying a 0.8ohm or one.2ohm mesh coil, the V