During the combustion of diesel fuel a great amount of soot is generated. Some of the soot gets into the lubricating oil with the blow-by gases. This is the type of material that tends to plug oil filters. Acids tend to form in diesel lube systems, caused by the combustion process and type of fuel burned. These, too, can shorten the life of oil filters as well as cause corrosive wear.
Raw fuel is more apt to get into the lube oil in diesel systems as compared to gasoline systems.
The fuel dilutes the oil and affects its lubricity properties. The importance of lube system service is apparent. Specified service intervals, in fact, are usually shorter than those for gasoline engines. Considering severe driving conditions such as short trips, long idle times and extreme engine loads, one can readily see the need for regular lube system service. The air filter requirements for diesel engines are similar to those for gasoline engines.