Note though it's not fuel cost we're taxing, but carbon, so more efficiently made fossil fuels would be cheaper and have less carbon tax, even if they are chemically indistinguishable from other fuels and contain the exact same number of fossil carbon atoms.

Things like, does the delivery truck have an efficient engine. Does the refinery use green or gray hydrogen to desulpherise the inputs, do they buy their fossil fuels from Norway vs Russia and so on.

It might only be a small difference but small differences across the whole economy is how the carbon tax is supposed to work.