Sorry, but 15W-50 is not 15 weight in the winter and 50 weight in the
summer.... it never had a calendar.....

junnie, no one ever said that. what was said is the 15w-50 oil pumps like 15
weight oil upon engine startup at ordinary ambient temps (and thus pumps
pressure to all bearings needing pressure oil MUCH more quickly than 50 weight
oil would) AND the film strength equivilent to 50 weight oil at engine
operating temps (which 15 weight oil would not).

junnie, it appears you are not all that familar why multi-weight oils were
developed nor why engine builders accross the board reccomend their use.