Introducing a thinner oil to an aging engine is a bit counter intuitive for wear and most inquiries into "30" weights seem to be strictly backed by the cost initiative alone. For how inexpensive (comparatively) it is to run a properly weighted oil, why even bother subjecting your engine to potential for failure? Just a thought.

For what it's worth, all of my diesels see synthetic oils: 15W-50 when doing long road trips through mountains, 5W-40 for regular use.
Do with that what you will.

__________________
Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....