So we seem to agree on this, and that's where I don't see the benefits of a thicker oil. Sure if there was a pattern of these engines running on thin oils not making it past 100k or 200k miles or something, I could see the argument, but right now people seem to be assuming there will be issues down the road when the data doesn't actually show that. The people who engineer the engines, and the oils, have more data from their real testing, than any anecdotal evidence we can find. Personally I have always run the viscosity that the manufacturers call for (except the car with a custom engine) and had no problem getting cars to 200k, but people like you who keep stuff longer than that, seem to be a dying breed. Cars are changing in design and technology faster than ever, and most cars will be too out of date for the majority of buyers, long before they reach their useful lifespan.