Horsepower is exactly what I'm talking about. Figuring it takes sixteen or so horsepower to push the air aside, overcome rolling friction and keep the car at speed, and 93 provides 400 horsepower, that's 4% of the available ponies. I don't recall how much horsepower is available with 87, maybe 345? That's 4.6% of the available ponies. As long as the cost per gallon isn't insane like it is now, 93 is cheaper to use on the highway.
Commuting requires very little power (at least for me), but still needs torque, I'm hoping 87 will get me there. The torque number is nearly the same for both octane ratings. It'll take a few tanks to see if that works.