Most of the tanks represented in game have an operational range between 50-150 miles, so fuel should never be a problem. Even if late-war maps represented German tanks running low on fuel, lets say they have at least have 5-10 miles left in the gas tank. You'd still be able to drive from one end of Kirovi Rog and back, and still have some gas left. So it's a moot point.
EDIT: As a nice touch, some very late-war maps that people are making could incorporate more broken-down/fuelless German tanks. Love the Panzerturm on Kriegstadt.