gather from various resources, one of those resources being shop manuals. I think you're better off making educated decisions about what specific oil to run based on your exact environment and car/driving conditions. Something to consider is that most of our cars are modified and could be operating at different temperature ranges than what was considered for the specs in the manual. With excess heat in (especially modified) TTs, a thicker oil is a good idea for maximum engine health. For colder cold-start enviornments, I don't think you can go wrong with a base of either 0 or 5. There are some merits to a thinner weight oil, such as more HP and better gas mileage, but I think most would agree that our bottom line is protection.