Ok... here is what I know (or at least what I THINK I know ). 1. GC base oils are very viscosity-stable 2. GC base oils are very oxidation-resistant. 3. GC has a robust additive package. Now... the $1 mil question: What component(s) of GC provides the dispersant / detergent abilities and TBN retention to enable GC to deal with thousands of miles of combustion by-products, moisture, etc? I am still trying to make myself feel comfortable with extended drains, and I'd like to know what components are working to keep my engine protected and sludge free over a long interval. IMO, Great base oils are one thing, but how does this really help keep combustion by-products "in check"? I am using GC, and we know a lot about it, so I figured maybe one of the chemist types could point to specific additives and give me a lesson.