Only if you can find out the viscosities of the 5W30 and of the oil stabiliser at two temperatures.
That still would only be acccurate assuming the 'stabilizer' acts like a normal oil. However I think that will be apparent from the viscosity data.
Here's a viscosity calculator for mixing any two oils. Mixing viscosities | Widman International
The viscosity of pretty much any oil can be found on the manufacture's website. Some are easier to find than others, but they all have it. It will be given at 40 C and 100 C.
If the temperatures are something different, go here to get the viscosity at any temperature.
(Note: the viscosities shown are typical examples. Enter the information for the specific flavor of oil your working with to be accurate). Graph your oils | Widman International
