Starting at the 0w weights, usually they are made of very high quality base stocks. They usually have lower HTHS and higher volatility than there 5w counter parts with the trade off of increased cold weather flow. All 5w40s that i know of are HDEO. Where it becomes complicated for me is the 5w30 vs 10w30 vs 10w40. If base stocks are equal, then the 10w30 requires less VII and would be more sheer stable and so on. The problem is they can make a decent 10w30 from lesser base stocks and even so with the 10w40s. I believe today all grades (common name brand) oils are constructed of at least grp 2 base stocks and most are solid oils. What you would need for extended drains really depends on your vehicle and driving conditions. I have seen used oil analysis of Pennzoil conventional at over 6k miles and look decent and also the same oil at 3500 miles that looks exhausted. Generally long drain oils have heavier add packs with extra antioxidants. Im not sure if this helped at all, maybe you could be a little more specific on what your looking for.
