I found that old TOD discussion here.

Basically it said the military use is 350,000 bpd but that DOD/DOE have overlap and there is alot of uncertainty surounding domestic/international use,etc.

The thrust of my question is more to perform a bottoms up analysis of the 84 mpbd of usage to see how much is really needed to make the current capitalist system run. If for example Venezuala decided to pal up with China and we lost that production and a few others, how much would we need to replace to keep things running at any price?

Basically, what is the US/Worlds fixed vs marginal oil usage?

I think it's pretty hard to predict what will happen if there's actual scarcity.  Once it's clear that there's an actual shortage, or that the price is only going to get higher, individuals, corporations and governments will start hoarding.  The military certainly will not risk being cut off; they will take more than they need, just to be safe.  

I don't know if the gas stations will go dry overnight as some predict, but it's a possibility.  Remember the chaos after Katrina, where people were filling up coffee cups with gasoline.  If everyone panics and fills up at once, the system gets sucked dry in days, if not hours.