Thanks.

I have found that Chevrolet is very secretive when it comes to its
factory-installed fluids and oils.

If you don't believe me, call Chevrolet and ask them these questions:

* What is the brand and what is the viscosity of the oil that came with
my new truck?

* What is the brand and what is the temperature protection of the
windshield washer fluid that came with my new truck?

One-Shot Scot wrote:

<<The statement "About a gallon" would be accurate from .6 to 1.4
gallons. Everything from .6 to 1.4 gallons rounds to "about a gallon".
Also, the  brimming capacity is not the same as the capacity at the fill
line. I would imagine the extra .33 gallon capacity is there to give you
the convenience of refilling the entire gallon jug without needing to
run the fluid unnecessarily low.>>

<<You do seem excessive in your need to exactly measure the antifreeze
portion of your fluid. I would recommend premixing your fluid and
marking the containers with the temperature mix, instead of agonizing
over the proper mix in the reservoir. For getting an accurate mix with
solution that is already in the reservoir, you would need to know the
precise mix and quantity of the old solution. Unless you keep an
accurate log of mixtures and graduate or siphon the reservoir to measure
the beginning volume, you will never get the accuracy you are talking
about.>>

Chevrolet customer service is unable to provide the capacity of the
windshield washer reservoir and the amount (if any) of antifreeze that
it originally contained. There is also the un-measurable variable of
summer evaporation of any methanol that the original solution may have
contained. Because of these unknown factors, I have treated the existing
solution as though it were plain water and mixed in the antifreeze
additive accordingly.

The difference of the previously unknown 1/3 gallon would have skewed
the antifreeze mixture table on the Mac/Valvoline antifreeze additive
upward by 20%:

Freezing Point ºF   Solvent     Water     VOC Limit
+28                            1                12             8%
+23                            1                 9             10%
+12                            1                 4             20%
+5                             1                 3             25%
-12                             1                 2             35%
-45                             1                 1             50%

From now on, I will premix the solution so that there will be no
guessing as to its antifreeze concentration.

Speaking of excessive needs, Mercedes Benz cars have Windshield Washer
Level Sensors:

http://www.discountmbparts.com/MB_Reservoir~Level~Sensor_list.html

So, has my Windshield Washer Reservoir tread been a complete waste of
time? I don't think so, because it has provided the following
information:

1. Owners of 1999-2005 Silverado/Sierra trucks now know that their
windshield washer reservoirs hold 1.3 gallons.

2. The owner of a 2004 Silverado reported that his factory-installed
windshield washer fluid did not freeze or slush up when the temperature
dropped to 0-5º F.

3. I have supplied links to websites which describe NAPA and
Mac/Valvoline windshield washer antifreeze additives which can be
custom-mixed down to whatever temperature protection is required.

4. We have heard from other posters who have had success with the
commercial products Rain-X, Prestone De-Icer and Blue Water.

5. I supplied a link to a homemade alcohol/detergent windshield washer
antifreeze formula.

6. And least, but not last, we heard from another
extremely-knowledgeable poster who's non-freezing windshield fluid
recommendations include "summer bug juice", "Whatever they sell at the
gas station, supermarket, wherever" and any solution selling for "$0.96
a gallon." "Bwahahahahaha!"

Those who can benefit from this information (particularly item #6) will
be better off for having read the posts in this tread. Apparently, those
who think that I am a complete idiot still read my posts for comic
relief. Therefore, everyone wins.

<<BTW it's much easier to drain the fluid out of the disconnected tap
hose than it is to siphon the thing.>>

<<My humble opinion, Justin>>

True. But I had the plastic tubing in the tool shed.