Protank 2 standard out of the box no improvements and factory coil, 3-4 mls per day.
Protank 2 with AFC and rebuilt 1.5-1.8 ohm coil using 30 g. Kanthal and cellu cotton, 5-6 mls per day.
Nautilus with factory 1.8 vertical coils, 8 mls per day.
Subtank mini with factory or own built 1.2-1.5 coils, 15 mls per day!
Little by little not only have my toppers become more efficient but I've also gone up in voltage/wattage and am now at a whopping 9-11 watts! Still a vigorously boiling pot of water will run out of water quicker than one that's at a roiling boil.
P.S. Retired at home every day and chain vape. When I do go out and "aboot", vape very little.