Which series of engine oils is specifically used in diesel engines?

The C series of engine oils is specifically designed for diesel engines. This designation signifies that these oils meet certain performance criteria established by the American Petroleum Institute (API) and are meant to handle the specific demands of diesel engine operation. Diesel engines generally require oils that can withstand higher levels of soot and contamination compared to gasoline engines.

C series oils are formulated with additives that enhance their detergent properties, viscosity, and total base number (TBN) – important factors for maintaining engine cleanliness and protecting against corrosion. These qualities are essential in diesel engines, which experience different operating conditions, such as higher compression ratios and more extreme temperatures.

On the other hand, oils not classified under the C series may not offer the same level of protection or performance necessary for diesel engines, making it critical to use the appropriate type of oil to fulfill the specific lubrication needs and comply with the manufacturer's specifications.