One surprising cause of an especially oily face is washing too much, and not applying lotion afterward. Your skin compensates for excessive dryness by producing more oil.
Our faces get oily easily and for many reasons. Touching, hair, dust, humidity, all play in. Try pulling your hair back, don't touch, and use oilfree cleaner/moisturizer.
In this type of skin, the oil producing sebaceous glands are overactive and produce more oil than is needed. The oil oozes and gives the skin a greasy shine