My 2019 Miata runs 0w20 in winter, 5w20 in summer 2 OCI per year. Completely amateur opinion here, every one has a opinion. Once on the highway it is running hydrodynamic in the bearings at RPM. That means the only friction on the bearings has to do with oil viscosity. The other issue is piston rings on the cylinder. Too thick oil will actually eat oil and reduce oil level. My oil level is zero loss per OCI. Same with my 2008 Miata too. Too thin and you will see iron show up on a DGA. Balance is the key. HTHS is another way to look at the thick or thin debate. Every engine is different. Being on the freeway means you do not have a lot of fuel dilution. The other positive of the lower viscosity is better heat transfer.