given that you live in michigan like I do, sticking to the 5W-30 will be just right. the reason is for all of our cold weather. the lighter weight (5W) means the oil thins a little easier to coat a cold engine faster.
the only change I would even think of making is in summer time I like to use a little bit heavier oil, 10w-30. with it's heavier weight, my heavy summer foot, and lots of two tracking and trips camping. I prefer the extra "gumption" that a 10w-30 gives me as a just in case sort of measure against the lighter 5W breaking down on me.
I also hear guys around here running a 10w-40 in the warmer months. but again these aren't street grocery getters, these are guys with guy trucks.
but even for just some light "playtime" a 5W-30 full syn. will be plenty to keep you clean and protected all year round. easier to remember too.
