Steve,
It would most certainly be measurable, albeit not worth the cost or effort. Viscosity grades run in defined ranges based, for sake of clarity in this context, on rate of flow at a specified temperature. Depending on what base
oil and what additives are used your concoction probably will fall toward the high end of the 5w range or the low end of the 10w range. Depending on which, it would be identified as what it measures too.
For added clarity, the test criteria for measuring viscosity are strictly defined methods and perameters defined by the American Society for Testing and Materials (ASTM) and utilized by the Society of Automotive Engineers (SAE).