cold weather oil
If you're from Minnesota(?), I wouldn't be so concerned with break in as much as cold start lubrication. You can always go back to dino in the summer. Block heaters are great - but remember that the oil is down in the pan (and lots of it) and it is basically at outside air temp. So sure you get a start with it plugged in, but 15W40 can be really thick at cold temps, so just because an engine starts in the cold, doesn't mean it should have been. You can spin bearings, burn camshafts, etc, due to the lack of lube on a cold start, even if the engine fires right away. Go 5W40 syn, plug in when it's cold, and your engine will be in better shape than if you didn''t use it come spring.
I live in northern Alberta, my truck has a diesel heater, and a wolverine oilpan heater, and of course syn 5W40. The closer an engine is to operating temp when it starts, the less cold weather wear it will experience.
These engines are meant to pull heavy loads up steep hills, so they have lots of oil and coolant, as a result it takes a long time to warm up all that liquid, so any help with syn oil, and warm fluids will be a big help to the engine.
