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Oil Groups

There are five groups of oil base stocks:


GROUP I - Solvent Freezing

Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some low budget automotive oils use Group I stocks, they are generally used in less demanding applications.

GROUP II - Hydroprocessed and Refined

Group II base oils are common in mineral-based motor oils, such as mid to high range products. They have fair to good performance in lubricating properties such as volatility, oxidative stability and flash and fire points.

GROUP III - Hydroprocessed and Refined

Group III base oils are subjected to the highest level of mineral oil refining of the base oil groups. Although they are not chemically engineered, they offer good performance in a wide range of attribute as well as good molecular uniformity and stability. They are commonly mixed with additives and marketed as synthetic or semi-synthetic products.

GROUP IV - Chemical Reaction

Group IV base oils are chemically engineered synthetic base stocks. Polyalphaolefins (PAOs) are a common example of a synthetic base stock. Synthetics, when combined with additives, offer excellent performance over a wide range of lubricating properties. They have very stable chemical compositions and highly uniform molecular chains. Group IV base oils are becoming more common in synthetic and synthetic blend products for automotive and industrial applications.

GROUP V - Additives

Group V base oils are used primarily in the creation of oil additives. Esters and polyolesters are both common Group V base oils used in the formulation of oil additives. Group V oils exhibit a wide variety of properties specific to each individual formulation. They are generally not used as oil products themselves, but add beneficial properties to other base oils.