I also witnessed a crash where a vehicle was going 80ish in a 55 zone on a beltline

Going 25+ over the speed limit on a road not designed for it is completely different than going 80 on a highway/interstate designed and built for that speed.

Fuel efficiencies aside it doesn't sound like you have a whole lot of confidence and/or experience behind the wheel (or you have a really really shitty car, your car should be able to handle 70-80 with ease), you should work on that.