It can be done. Make sure it is labeled USP. Three things will happen when you mix it with your liquid:
-Your liquid will get thicker. It may not flow well in your PV.
-The flavor will dilute. You will get little flavor from your liquid.
-The nicotine will dilute. You will get far less satisfaction from your liquid.
I suggest purchasing 100% VG
eliquid from the supplier you got your last liquid from. If you
buy it in the same flavor and nicotine content, you may mix freely without losing flavor or affecting the nicotine content of your liquid. If you can't get it from the same supplier, try getting it from another supplier and use a similar flavor. If you mix small batches, you can determine which mix works best for you and simply order that mix from now on.
Good luck, I shall drink to your success
