How often should the oil be changed?

Engine oil shall be changed in accordance with the instructions of the vehicle manufacturer. As a rule, it is changed each 10–15 thousand km travelled. However, the situation is not simple as it seems. Changes in oil properties depend to a large extent on road surface quality. Travelling on city roads and highways differs dramatically; in particular, this is the four-fold difference in service meter hours. Let's say that about 700 hours of lubricant operation per 15 thousand km are needed under city conditions, while travelling on highways requires no more than 200 hours. It is important to understand that the vehicle engine is exposed to different load levels under different conditions. Less the load, less change of oil.