Mobil 1 Advanced Fuel Economy 0w-8 - Canada

I guess it all works out as long as manufacturers don't do significant changes more than once a year.

Given that the Americans have decided to have model years, then most model years transitions can be placed at whatever point in the calendar year the marketing guys like, without a production change; but if there's a production change in a calendar year, they would align the US model year transition with it - whereever it actually is in the calendar, even if it means the "years" either side don't last anything like a year.

(Which is what you said in the next paragraph that I skimmed too fast and didn't quote...)

But occasionally there will be unexpected stuff - like the door switches, that don't fit into that.