I don't quite follow you, but I've used the phrase "boutique oil" to describe some oils on the market that are typically high-priced and sometimes over-hyped. Most are not commonly seen in stores and some are largely a mail-order item.
By that description M1 15w50 would not remotely fit that description. It isn't really a "car engine oil," but an "engine oil." There's too much emphasis placed on application-specific labels (like "V-Twin," etc.) and there just isn't enough difference between an air-cooled MC engine and a car engine, air- or water-cooled, for there to be a specific oil earmarked for them. These oils are largely put on the market to sell at higher prices to people who think they're getting something extra, but based on tests I've seen they are not.
I had a long talk with an M1 product engineer at a racing event about a year ago and he told me what I already knew, that the MC-specific products are largely a marketing phenomenon, and that all synthetic oils on the market today are fine products. There are too many government and other specifications that must be met and they all must meet them to carry their specific labeling.
For example, I have two friends who did big-bore upgrades two years ago on their EG's, one using M1 15w50 with 60k miles and the other Amsoil 20w50 MC oil with 50k miles. Upon inspection of pistons, jugs, and top-end wear points both engines had no visible or measurable wear--and the components looked identical. I was amazed to see the factory hone marks on the cylinders, and even the piston coating was intact.[/QUOTE
You may have missed his (lol) re: botique oil.
