Gas Milleage for Excursion 2WD Versus 4WD

I am looking at a 2001 Excursion with 88K miles and it is a 2WD. Does anyone know the gas mileage city/highway for the 2WD versus the 4WD? Thanks for any help.

I couldn't find Excursion, but here is Expedition for that year. 2WD 13 city 18 hwy, 4WD 12 city 17 hwy. So not much difference between 2WD and 4WD. Excursion will be less.

If those are manufacturers estimates you can expect worse in the real world.