Castrol, Valvoline, whoever will have PDS on their website for the product line.
You'll be looking for viscosity at both common stated temps, 40c and 100c.
Take this for example... Valvoline Conventional
Now head on over to the viscosity calculator HERE
and plug in the percentages of the two oils, and the viscosities.
Now you can compare that with the chart on the BITOG homepage, Get yur visco info heah....
You can also use this info to blend up oils from AZ, AA, and OR sales to get a workable viscosity for your application. Say, thinning out some .33 a quart 20w50 for something that can run a 10w30. (Yes some of us are still working through a stash of really cheap 20w50...)