Oil viscosity - why the 20W-50 BS?

What Joe said, for the most part.

There are instances where special oils are needed. But for the vast majority, nothing fancy is fine.

My 97 Neon had it's oil and filter changed in November of 2010. It's got about 200K on it, I bought it at 67K in '02. It's had about 7 oil changes in that time and gets 30+mpg. My truck, last dropped in October of 2010. My '65, I've owned since '09 and still has the oil and filter it came to me with in it. I hate changing oil.