I've been looking at some UOAs and they all seem to end up around 11 to 12 cSt, even during a short OCI on standard naturally aspirated, port injected engines. To me it would only be a rare occurence caused by specific engine designs or fuel dillution in direct injection engines. Do all euro 5W40 have the tendency to shear into a 30 grade quickly? What are the causes? I've used this type of oil a lot but it looks like a euro 5W30 would do just as good and not shear as much since they have a thicker base and less VII.