Moving in parity with combat vehicles, that would mean an infantry unit in combat would use 0.4% of their total mass in fuel, and 0.2% in non-combat operations. This would allow them the same operating periods as combat vehicles, and the same peacetime operational tempo with a 4x capacity monthly allowance.
However, that would mean a motorized platoon would consume only 12kg of fuel during a non-combat maintenance period, which is below the threshold of most game accounting, I'd imagine. Even a mechanized/tracked unit, as the heaviest infantry unit, would use 112kg of fuel during a combat period, less than half the previous value.