Monograde oil is a type of lubricating oil that is designed for use in systems that operate at a single temperature range. It is made from a single base oil and is formulated with a specific viscosity, or thickness, that is appropriate for the intended temperature range.

Monograde oils are typically used in systems that are not subject to wide temperature fluctuations, such as in engines that operate at a constant temperature. They are also often used in systems that are designed to operate at a specific temperature range, such as in gearboxes or bearings.

One of the main advantages of monograde oil is that it is relatively simple to manufacture and is often less expensive than other types of lubricants. However, it is not well suited for use in systems that are subject to wide temperature fluctuations, as the viscosity of the oil may change significantly as the temperature changes. This can lead to reduced lubrication performance and increased wear and tear on components.

In contrast, multigrade oils are designed for use in systems that are subject to wide temperature fluctuations. They are made from a blend of base oils and are formulated with a viscosity that remains relatively constant over a wide temperature range.