-20 Celsius and the flow is about half of what you saw in the picture. Can't really tell by the feel when your hand is submerged in -20 coolant....but I can tell just the same. The pump, however, is still quiet and cool so it's not working hard. May have to cut 4 more grooves in the block soon.
I could thin it with some water perhaps.....it is ~ half anti-freeze and half washer fluid.
I guess the flow isn't so bad yet.....
