Periodically homeowners tell Stormworks that they have a tank full of oil and they would like to sell it. As it happens it’s a rare occasion when a tank has pure oil in it. Homeowners usually burned most of their tank oil before switching to gas, or had their oil delivery company pump out the oil.
Oil found in old unused tanks has all kinds of issues. Water accumulates in a tank over time as well as bacteria. Often what is perceived as a full tank is oil floating on top with water and sludge at the bottom. Nowadays removing small amounts of oil and polishing it to move to another tank is not economically feasible.
Large commercial tanks with thousands of litres of oil can have some value, but the fuel needs to be polished and the water removed before being fit to use.