[grumpy in NH]

M1 is not "chemist jargon" synthetic, just a marketing term "synthetic" and does NOTHING GOOD for you in moderate climates. The much touted (by mobil) PAO base is an inferior lubricant at high temp. M1-EP is synth but who knows what's in it. If Di-Ester polar molecules are not employed at 10% or better blend, then forget it and stick with DINO oil. Molecular diversity is actually GOOD for lubrication in moderate climes (long chain for journal hydrodynamic and short chain naptha derivatives for piston skirt and ring pack and valvestem boundary lube. The problem is API-SM oils are "crap" compared to most Manufacturer spec European LL oils, mainly through moderation of boundary and dry lube metal salts in the addpack (due to "early" poisoning of catalyst and afterburner honeycomb). Only proven good synthetic are Motul 300V and ELF Excellium and Fuchs. Then there is Redline and I am unaware of its constituents - your research on this one. As a lower cost alternative, please take at look at Superbike motorcycle high specification oils - some of these should be adequate (meaning better than SM API). Check out site like kneedragger.com