Issue link: http://read.dmtmag.com/i/859318
Engine Oils Background & Properties castrol.com/GPS 800 255 4417 May 2025 GPS Industry Specifications • Rust and corrosion inhibitors protect metal surfaces from water-related wear. Improper rust protection can result in significant corrosion in transmission or final drive gear. Rust and corrosion inhibitors protect components by forming a protective layer on the component or by neutralizing harmful acids. • Found primarily in heavy-duty transmission fluids, greases, and gear lubricants, extreme pressure (EP) agents are a special type of anti-wear agent in that they protect against metal-to-metal contact but under extreme loads and temperatures. EP agents must be monitored carefully because they may have compatibility issues with other active chemicals in the lubricant and with yellow metals, such as copper and bronze. Other trade-offs include hydrolytic stability and frictional characteristics. • Friction modifiers work to improve the overall efficiency of a lubricant by decreasing friction, preventing scoring, and reducing wear and noise while adding some fuel economy. Performance Additives Specific to temperature performance, these additives are essential in lubricants whose applications are subject to wide temperature ranges. Lubricants with improper tolerance for temperature, both environmental and operational, can cause a host of problems with pumpability, cold starts, and wear. • Viscosity modifiers boost a base oil's natural viscosity index (VI) as well as extend lubricant performance over varying temperatures. Viscosity modifiers work through a unique method of selective oil thickening. High temperatures result in more thickening, which reduces the likelihood of wear; and low temperatures result in less thickening so a lubricant can maintain pumpability. • Pour point depressants are targeted specifically toward enhancing low temperature flow characteristics. Oils tend to form wax crystals during low temperatures. A pour point depressant prevents oil molecules from "sticking" to wax crystals, which would inhibit flow. Some viscosity modifiers also function as pour point depressants and vice versa. Protective Additives Different from surface protecting additives, protective additives focus on preventing breakdown from foam, oxygen, or water. Due to the severe duty endured by most diesel applications, protective additive packages are a distinguishing factor among finished lubricants. • Anti-oxidants protect against oil breakdown due to oxidation. Under conditions of high temperature and severe service, oxygen can mix with the churning lubricant at high temperatures and oxidation occurs. An- ti-oxidants or oxidation inhibitors act like a sponge to extract oxygen from the oil and slow the oxidation process. Anti-oxidants are used in almost every heavy-duty and automotive lubricant. • Foam is the result of air getting trapped in the oil. Anti-foam agents repress foaming by lowering sur- face tension and allowing trapped air to escape. Excessive foam can lead to a breakdown in an oil's film strength and eventually causes extensive wear. Like anti-oxidants, anti-foam agents are found in almost every commercial lubricant. • Metal deactivators are actually a class of oxidation inhibitors. Primarily used in transmission fluids, metal deactivators protect metal surfaces from additives that may be corrosive. • Emulsifiers and demulsifiers are engineered to handle water contamination in a lubricant sump. Emulsi- fiers eliminate any free-circulating water by enabling oil and water to mix. Demulsifiers separate water from oil. If maintenance practices call for water removal, then demulsifiers are the additive of choice. When there is no opportunity to remove water, emulsifiers are added to the lubricant. A23 ecastrof