Originally Posted By: NormanBuntz
Would that calculate to a 5w-23.33? Just curious.
Not really as there is no such thing as 23.33 grade.
You need to look at the actual 100C viscosity of each oil, and then average it out in the right proportions to see what number you get. Then see whether this resulting number is still in the 20 grade or already in a 30 grade. Most likely it'll still be a 20 grade, albeit close to 30.