I just read the initial post and have a question/observation. If the static sample at the testing lab contained 1.23% antifreeze, there should have been water detected also, I believe.
I don't think it's overkill if there is a coolant leak that you're not planning on or not able to fix for a while. Yes they were developed for those engines with intake gasket leaks, Northstars etc and we used them a lot back in the day when I worked at dealerships.
In this case I have a confirmed leak and in a few months I'll get another uoa to see what affect the seal tabs and switching to water had on it.
I just read the initial post and have a question/observation. If the static sample at the testing lab contained 1.23% antifreeze, there should have been water detected also, I believe.
Good point and I don't know the answer. One possibility I can think of is that the water is evaporating a lot easier than the antifreeze? The truck gets a lot of hours of run time, idling for AC and highway driving and driving from one job to the next. Depending on the day it may have 4 hours of run time for a 9 hour day so it's unlikely to have a lot of fuel dilution or moisture buildup (short of the coolant leak).
One of the reasons I initially suspected this besides adding some coolant every now and then was the catch can was getting a ton of milky looking water when the weather was colder still. With the hot weather that isn't happen anymore and the oil on the dipstick always looks good even just before an oil change. Also no buildup under the oil cap.
