There is an argument for that, but I doubt though:-
a) anyone has done the comparison;
b) anyone on here has the time or technical capacity to do it accurately and come out with a result that would stand up in court;
c) Could commision someone like Ricardo to do it, probably quote about £150,000 or so to do it comprehensively enough to be worth it;
d) if you advance to the correct setting and you find you can't pick-up 98 Octane, you'd be in trouble;
e) running on lpg, its possible to use the original timing, so I'm told, as it does indeed have a high enough Octane rating. Not sure if anyoen does though... so this might compensate wholly or partly for lost mpg on lpg (!)
gallons?
Why not - do your really want to have to invert the whole thing and talk about litres per 100 Km or some such daft construct.
If there's a prob converting from litres to gallons, just remember one number
0.22
It's reciprocal is 4.5454545454545454545454545454545
what would you rather remember?
Or for rough mental calcs use a factor of five and then take 10% off.
A gallon is a nice manageable sortof quantity anyway, petrol weighs about 8lbs, water just over ten and a cubic foot of water about 65 lbs (just 1% more than 2 slugs, the true imperial unit of mass). Litres and cubic metres - pah! Kilos? Well, I ask you, how can that compare to the noble British slug?
PS. HackBobSaw - Yea, I know
