I think your analogy of gasoline consumption to chlorine PPM is a bit off. As long as pH is controlled properly there isn't much change in sanitizer residual (assuming the feed rate is capable of keeping up with demand). I would suggest that gasoline consumption be equated with sanitizer consumption instead. Higher bather loads require more sanitizer to keep sanitizer PPM and ORP steady.
Other than that I'd say you were spot on.
With Data logging of your ORP and Residuals in a pool, you will find that a steady orp will yield residuals as low as 1ppm, and as high as 3ppm...given a pool with HEAVY use...on the norm, the residual does remain quite steady.