Lou, I think the issue here is how long it will take to switch out the vehicle inventory. Estimates I've seen say on the order of 15 years. Of course, that might speed up a bit if the prices go skyhigh and the more efficient vehicle supply can meet rapidly increasing demand.

As far as people "bitching" about "people won't conserve energy" goes, I agree--what else are they going to do? But this too will take some transition time. It won't happen overnight. I take it you're not a big believer in Jevon's Paradox.

But geopolitical oil shocks are the wildcard. And anyone with a functioning brain and a little imagination will have little trouble thinking up disasters that could happen. If that Al-Qaeda attempt at Abqaiq hadn't been such an amateur job, this week would be very different than it is.

It occurs to me that there's a big difference between "registered" and "on the road".

This is highly significant, because all the old econoboxen used as winter cars could easily become primary vehicles overnight.  The guzzling trucks that people commute in today could wind up parked most of the time.  What difference does it make if a vehicle is registered, if it isn't driven?  Reverse the current vehicle preference, and fuel consumption would fall without any change in what's "on the road" measured by registrations.