I read somewhere that nicotine isn't actually addictive by itself in e-liquid. It's only in combination with some cigarette ingredients that it becomes addictive. So I'm testing this.
Normally, I vape 18mg nicotine liquid, probably around 4 - 6 ml per day. I bought some 0mg nicotine liquid. I'm going to vape it exclusively for the next few days and quit the nicotine cold turkey.
So far, I've gone through the entire day on 0mg. I haven't had any withdrawal symptoms at all. The only thing I've noticed is that the liquid is smooooooth and delicious now...And I actually prefer it without the nicotine, go figure.
Registered nurse reporting in: I actually did my Bio-Sciences thesis on this

nice observation, this is one of the first things I noticed about vaping myself is that the nicotine just felt different. There's alot of things I discovered studying this, however no empirical studies have ever been recorded on this (I wonder why *cough* tobacco companies). It all boils down to Acidity, Sugar derivatives, and added "freebase nicotine".
-Acidity: The nicotine molecule found in nature and our vaping juices are almost always positively charged, they have alot of protons that make it "harder" to be absorbed by the lungs, and this is for a good reason because the lungs don't want a certain amount of positively charged molecules in our bodies, most of them are harmful.
Ammonia, is an additive found around the world in cigarettes, and most have heard it in anti-tobacco commercials even. This high strength acid strips protons off the nicotine molecule to make it more easily absorbed by your lungs, what the companies try to do is "match" the acidity of our lungs to make almost all of the nicotine absorbable. Taking the + charge down is unnaturally allowing nicotine molecules into your body, and allowing the molecules to squeeze in where nature didn't intend (and for a good reason).
-Sugar additives: This may sound harmless but really could mean anything, which derivatives aren't known, dopamine is a sugar derivative but we all know ....... isn't exactly good for us. The common sugar derivatives are used to enhance the level one MAOI neuro-transmitters in the brain, which like the nicotine, and coincidentally MAOI/level one neuro-transmitters are extremely high in cigarette smokers, and many suffer depression from that imabalance. I personally think, after going through it myself, and having level one medication fix my depression, that's exactly what they're designed to do: enhance the nicotine transmitters that make us "like" or be addicted to nicotine.
-Freebase Nicotine: It's exactly as it sounds, chemically isolated nicotine, that's designed to go straight to the brain with hardly any interruption from the lungs or neuro-transmitters, alot of these are found in nicotine gum and patches etc. These are actually known by the scientific community to be added to cigarettes, camel: 2.7% Marlboro:7% I've tried both of these cigs and I can definitely tell these %'s are accurate. And freebase nicotine is like the "crack" of tobacco nicotine, super efficient, super addicting, and very absorbable. I wouldn't be surprised if some companies were basically soaking nicotine-less tobacco with freebase nicotine because it would be cheaper and more addicting.
-These were my thoughts on it, and alot of it is backed up by empirical evidence. Just thought I'd share this with you guys.

It's a scary business the tobacco companies are running.