Oil, Diesel and Kerosene
From Desert Operations Wiki
Oil, Diesel and Kerosene is needed to attack other players. This is why the are put in the same category. Oil is a very scarce commodity in the game and it is wise to concentrate on the construction of Oil refineries. The Diamonds can be exchanged for resources, you also receive a little every 10 min depending on the amount of Buildings you have producing the resource. The amount you receive from the building can be seen under the "Income + Expenses".