Viscosity: The "15W-40" designation indicates the oil's viscosity, which is a measure of its resistance to flow. The "15W" part means that the oil has a viscosity grade of 15 in cold temperatures, making it suitable for use in colder climates. The "40" indicates its viscosity at higher temperatures, which is typical for engine operating temperatures.

API Classification: The "CI-4" specification refers to the American Petroleum Institute (API) classification system. The API CI-4 classification is specifically designed for diesel engines and is intended for engines built to meet emission standards implemented around 2002. CI-4 oils are formulated to provide enhanced performance, including better soot control, improved wear protection, and increased resistance to oxidation compared to previous classifications.

Applications: 15W-40 CI-4 lube oil is primarily used in diesel engines, particularly in heavy-duty applications such as trucks, buses, construction equipment, agricultural machinery, and industrial machinery. It provides lubrication, protects engine components against wear and corrosion, helps to maintain engine cleanliness, and assists in managing engine temperature by dissipating heat.

Properties: CI-4 oils typically have properties that allow them to withstand the harsh conditions of diesel engine operation, including high temperatures, high pressure, and the presence of soot and other contaminants. They are formulated with additives to improve viscosity stability, enhance detergent and dispersant properties, and provide anti-wear and anti-corrosion protection.

Maintenance: It's important to follow the manufacturer's recommendations regarding oil change intervals and maintenance practices when using 15W-40 CI-4 lube oil. Regular oil changes are essential for maintaining engine performance and longevity.