(4) 1-oz bottles (of 48mg) = 118.28 mL.
Converted to 12mg, you'd have: 48mg /12mg = 4 ... 4 x 118.28 mL = 473 mL of 12mg juice.
You'd need 12 oz of doubler to make this much 12mg juice and that's what you have.
Stretched out over a year, it amounts to just under 1.3 mL per day.
What you wanted:
48mg at 30% VG
Doubler at 50% Vg
Juice would have been 45% VG. 30% + (50% x 3) = 180... 180 /4 = 45 > 45%
What you got:
48mg is 10% VG
Doubler is 30% VG
Juice comes out at 25% VG. 10% + (30% x 3) = 100... 100 /4 = 25 > 25%
So, it looks like you need to add an additional 20% VG to the mix.
You might find that more flavoring is unnecessary. The difference in taste will be noticeable, but flavoring is responsible for some of the throat hit. My Tasty Vapor Tin Box Mint was super strong in taste and I ended up adding 50% unflavored 24mg VG base to tame the mint.
You might try using 25% VG and this would simplify mixing:
1 part 48mg juice
2 parts Doubler
1 part VG
I've seen big medicine droppers for children at Walgreens, and this could work well for measuring your proportions.
Live a healthier life - Walgreens
I usually suggest that DIYers thin their VG before using it in mixes, for several reasons:
1) it's much easier to measure (100% VG is as thick as honey)
2) thinning is a necessity if you use cartomizers
3) it's more consistent to thin in a big batch
4) it simplifys calculations
5) it reduces steeping time slightly
To thin VG down to the viscosity of PG:
4 parts VG
1 part distilled water
Warming the container of VG helps thin it for pouring and mixing. Heat a pan of water to boiling then set it aside for 2-3minutes to let the pan's bottom cool slightly. Stand the bottle of VG in the pan and let it set for 10 minutes or so. Remove the bottle and wrap it with a kitchen towel to hold in heat and protect your hand. Loosen the cap carefully in case pressure has built up in the bottle. The VG should pour easily now.
If you do decide to add more flavoring I suggest getting that advice from DIYers who have used wintergreen, because I have had very little experience with it. Maybe you could start another thread with a title like: "What's your favorite Wintergreen flavoring?"
Good luck Keesie, and I hope this helps!