Joys of Multigrade
A lot will depend on your operating conditions particularly temperature. Here in Blighty, multi grade 15/50 works well all year round, so no need to mess around when the seasons change. As soon as my new Lycoming was run-in, I went for Aeroshell product and 850 hours in, not missed a beat. A big plus is that it complies to Lycoming spec to allow unleaded to be used, so I can use UL91 if available (and if competitive!).