All the highways here in Michigan are 70mph i.e. 112kph, but you can always get away with at least 80 (128 kph) and most of the time 85-90mph (136-144kph) without worry.

To be fair, on the 400 series of highways it's almost always fine to do 125 without worry of being pulled over. 130 they don't often bug you either if the road conditions allow it.

I've driven some of the 80mph highways out in the AZ/CA area of the states and it's pretty nice doing 90-95mph without worrying about getting pulled over.