An Article on Tire Pressure
 

This article is written for bikes but would translate over to cars. It covers various loads, rolling resistance, pressure, etc. I found it interesting, perhaps you will also. It is written by an engineer. Here is a link:

http://www.bccclub.org/documents/Tireinflation.pdf

I generally think of myself primarily as a cyclist. It's interesting to see the cycling world move toward bigger tires and lower pressures after so many years thinking that skinny tires and higher pressures were the key to efficient riding. And I'm on board -- my favorite bikes have high-quality 38-42mm tires at Berto-approved pressures, and it doesn't seem to slow me down.

I think the difference is that while some energy is no doubt lost when a car's suspension bounces, the engine's output isn't nearly as affected as a bike rider's. :)

Frank Berto! Great guy.