After using diesel engine oil for a period of time, due to the infiltration of external impurities and oxidation reaction, the lubricating performance of the oil gradually loses, and it must be replaced in time (the oil changing cycle is stipulated in the diesel engine operating manual). In the following cases, due to the poor working conditions of the engine, the oil change cycle must be shortened.

1. Vehicles running on roads with more dust and sand, diesel engines operating in dusty environments (such as threshing, rice milling, grinding, feed crushing, etc.), worsen the wear of diesel engines because more dust enters the cylinder through air filters, and these impurities enter the oil pan and pollute the oil.

2. Diesel engines often operate in wet environments (such as pumping) are prone to condensate water droplets in crankcase, and water droplets penetrate into oil, which can easily cause oil emulsification and deterioration.

3. Diesel engines often operate under small throttles and light loads. Diesel can not be fully atomized and burned, and it is easy to flow from the cylinder wall to the oil pan and dilute the oil.

4. For diesel engines operating in cold areas, diesel in cylinder is easy to coagulate and mix into oil, which reduces the lubrication effect of oil.

5. Diesel engines often operate in coastal areas, because of the high concentration of water vapor salt in the air, the corrosion of diesel engine parts is accelerated, and the engine oil is liable to deterioration.

6. Diesel engines, which often operate under full or overload conditions (such as broken stones), are prone to oxidative deterioration due to high engine temperature and high carbon deposition.

7. During the running-in period of a new or overhauled diesel engine, the mechanical impurities in the oil increase due to friction and wear, and the oil must be changed early.

8. Before the deterioration or overhaul of the technical status of diesel engine, due to the excessive matching clearance of the relevant parts in the cylinder, poor combustion of diesel engine, increased carbon deposition, high-temperature exhaust gas is easily channelled into crankcase, resulting in the oxidation and deterioration of engine oil.

In addition, when diesel oil and cooling water infiltrate into the oil pan, or when the accident happens, the oil must be replaced in time and the lubricating oil circuit must be cleaned.