The range of all vehicle gets signifigantly reduced to reflect ranges of their real life counterparts. Scaled down to match the relative short distances in Arma. A full vehicle on mission start should still most likely never need a refueling during a mission.
APCs and Tanks now share a muzzle for all ammunition types of their main guns. This prevents an exploit that skips the reloading time of a round or clip while changing the ammunition type. Also makes it possible to switch between ammunition types using the scroll wheel like in Arma 2.
MBT main guns and mortars can no longer lock on enemies. The AT rounds of both now have raised cost values to encourage the AI to not use those rounds against foot soldiers over their machine guns or HE rounds.