question???? how adverse an effect will the lower viscosity of the 10w have on these old engines which were designed for the 30w oils??? It seems to me that you will get greatly increased wear unless you severely tighten up the bearing clearances (every where) since the lesser thickness of the weight difference will allow the parts to run(force) themselves together and wear faster than normal. You chemical/mechanical
enginers out there PLEASE respond with your knowledge. And the 10w will get thru parts/seals and burn off much faster. YES???NO????
