Just to keep the discussion in perspective;  I have been using Texaco
10-W40 on my 85 Vanagon from 50k miles when I bought it to its  current
140k miles, changing the oil and filter about every 6k miles.  I have
never had to add oil between changes and it has never been down more
than 3/4 of a quart at the oil change.

These engines do not seem to use much oil either petroleum or synthetic
based if cared for.  I suspect it has to do with the valve stems being
horizontal rather than vertical.

Larry Stichweh