Monograde oils are designed to be used within a defined temperature range. The monograde oils are classified by the thickness (or viscosity) of the oil. The intention is to ensure that the oil will cycle as required under specific operating conditions. In cold climates a thinner grade, e.g. SAE 30, is more likely to be required whilst in warmer climates a thicker grade e.g. SAE 100, is more likely to be selected. They can also be characterized by the presence of an additive package ("AD" or ashless dispersant oils) or the absence of such performance additives ("S" or "straight" oils).