One of the first lectures in an econ class is about opportunity cost. Everything- material or action- has a dollar cost associated with it. If you gotta get there fast, the cost is extra fuel. If you don't gotta get there fast, the cost is extra time on the road. Which cost is less "costly" depends on the person and situation.

You've done 70 and 85- care to try it at 55? I notice a large upswing dropping from 65 to 60 to 55, and it seems to level out there, since lockup is at 48 anyway.