Well I don't want that much of a dirt
What I mean is in a woodland area turret shouldn't get dirty with dust/sand, however the bottom certainly will
Here's a screenshot from Steel Beasts Pro
And here's reality
(it's hard to find a good photo with M1A1 getting dirty after operating in a woodland area)
As you can see there's some dirt over the tracks but the top of a tank is relatively clean since it's no desert where the tank can kick up a lot of dust.