Mick, if taxes were that easy, you wouldn't need me to do them for you.
It has to do with air-fuel stoichiometry. Let's just for the sake of argument suppose that at stoichiometric ideal the engines would require 108% of 21L to cross the finish line. Let's say new Assen is 102%. Aragon is 105%. Jerez is 100% (ideal). Mugello is 97%. etc etc etc. If they decrease the race distance by 5%, they'd be knocking Sepang down from 108% or 8% lean to 103% or 3% lean. You can't say that is equivalent to running a 22L gas tank for the entire season which is the conclusion people are trying to extrapolate from the on track events. It's more like running a 21L tank at a new Assen or some other circuit that isn't terribly hard on fuel.
The teams don't want to run the engines lean if they don't have to b/c it increases heat and kills reliability. Let's just suppose that the engines don't like running more than 5% lean. If the race is 105% at optimal air fuel, and you add 5% fuel, the teams get more revs and more power b/c they will continue to run at 5% lean. If the race is 110% or 10% lean, they will rich the mixture to save the engine without drastically increasing the performance.
That's how it works. Imo, the reduction in race distance has the same effect as running a 21.5L tank at all circuits or something like that. If they ran 22L or 24L, imo, Honda would wind their engine up to the max and blitz the field. They wouldn't use the fuel to rich the mixture at any of the circuits, they'd simply turn up the wick to 20,000rpm and then let their superior reliability win the day.
