14.5 gallon tank. All golfs use the same fuel tank whether it be a gasser or a tdi. There is a space in the tank for an air bubble to compensate for the different volume of gas based on it's temperature, so your tank doesn't overflow when it's filled up and it gets hot outside. Diesel fuel does not expand nearly as much as gasoline when it gets heated, therefore the air bubble is not needed. VW actually puts a button inside the filler neck of the tdi's that, when depressed, allows the air to exit the tank allowing for almost two more gallons of fuel to be put in bringing the total capacity to somewhere around 16.4 gallons. I usually run till my low fuel light comes on, right around 700 miles, and it usualy takes about 15.5 gallons to fill it back up. Anyone learn something new today?