Is this for the Armortek M4A3 or your scratch built one ?
My ref for the M4A3 says that the one inside the turret splash guard is fuel for the auxillary engine, the one on the centre line is for the main engine oil and the other four are for the left and right main fuel tanks.
Assuming the M4A2 bit means it's the same layout, the one inside the turret splash guard is the same - auxillary engine fuel. I don't know if this was petrol or diesel on the M4A2 - I would imagine it was petrol, which seems like a logistical nightmare to me !
The ones inside the half-moon cowls are the diesel fuel.
The ones inboard of them are the lubricating oil.
The ones to the rear of the lubricating oil ones are for water.
The one in the middle of the deck but the other side of the engine grills apparently covered the two engine oil gauges.
A good pair of books to get are the Armor PhotoGallery ones on the M4A2 - the second one (76mm Gun Tank) covers the Easy8.