Some lubricants are incompatible because of differences in additive chemistry that lead to undesirable chemical reactions. Others change the lubricant’s chemical properties or are added for cosmetic purposes. Some additives affect the physical properties of the finished lubricant. The choice of additives and the balance among them differentiate an antiwear hydraulic oil from a turbine oil, for example. Deposits may form because of additive incompatibility or seal compatibility may be compromised.Īdditives impart special performance features to the finished oil. Even then, compatibility is often concentration-dependent. The limited exceptions include some PAO and ester-based products. Lubricants made with synthetic base stocks should not be mixed with products made with mineral oil, even if they are designed for the same application. Synthetics are used where the value of their special functional properties, oxidation stability, fire-resistance, etc., outweigh their cost. Polyalphaolefin (PAO), organic esters, glycols and phosphate esters are examples of synthetics that are used to meet specific needs. Synthetic base stocks are made by chemical manufacturers to impart special qualities to the finished oil. They are relatively low cost, generally good solvents for most additives, available in a wide viscosity range and compatible with a number of seal materials. Most lubricants are formulated with mineral base stocks that are severely refined, low-wax, heavy distillate fractions of crude oil.

They carry the load in hydrodynamic lubrication, remove heat and debris from friction and wear and help seal out contaminants. The base stock is the oily portion of the lubricant, chosen for the physical and chemical properties needed in the final blend.īase stocks, in most industrial lubricants, are selected based on the requirements for viscosity, oxidation stability, fire-resistance, biodegradability and water miscibility in the final product. Most performance lubricants are a blend of base stocks and additives. To understand why some mixed oils are OK but others are not, one must understand how modern lubricants are formulated.

Deposits may form that could increase wear and plug filters. Mixing the same API grades of synthetic passenger car motor oil and mineral oil-based engine oil won’t damage the engine, but you will lose the performance features you expect from the synthetic.Īt the other end of the spectrum, adding typical turbine oil to an antiwear hydraulic oil in a hydraulic pump could spell disaster. In its mildest form, mixing different lubricants may lead to a degradation of lubricant performance. Your response to a situation where different lubricants are mixed will depend on the products in the mixture, the end-use application, the relative concentrations of products and the total volume involved. Don’t be afraid to bring in an expert, whether it is the lubricant manufacturer, the additive supplier or an independent consultant to your site. If it occurs accidentally, address the problem immediately. When in doubt, don’t mix different lubricants. Mixing lubricants is fraught with danger - to your equipment, to your business and to your wallet. The old saying, “oil is oil” no longer applies. Modern lubricants are sophisticated products, formulated to meet the demanding lubrication requirements of modern equipment. Mechanical problems leading to shorter equipment life can occur, sometimes catastrophically. When lubricants are mixed, this balance is often upset. Today’s high performance lubricants are specifically formulated with a carefully selected balance of performance additives and base stocks to match the lubrication requirements of the equipment in which they are used. Managing the risks of mixing lubricants is critical.

Mix base with water