This calculator can give you some idea of what a blended oil would be like. I used this for awhile, blending M1 15W-50 with M1 0W-20, then later on M1 0W-20 and Delvac 15W-40. Then, like you, I decided to just pick a good oil and stick with it. I've got approximately 40 quarts of GC ready for my car as soon as my free Maxlife synthetic is done.