After the end of the running-in process, the normal operation stage begins, the duration of which depends not only on the design features of the engine and the car as a whole, but also on the operating conditions and the degree of compliance with the basic requirements for car maintenance. During this period, the engine power, specific fuel and oil consumption and oil pressure in the system remain approximately at the same level, and the operation of the car does not cause any special problems. The duration of the period of trouble-free operation is up to a mileage of 60-80 thousand km.
During operation, due to natural wear, gaps in the joints of the moving elements of the engine increase, the oil pressure in the system drops slightly, and the specific fuel and oil consumption increases. These processes occur most intensively at the end of the engine's warranty period (for Japanese cars under normal use after a mileage of about 10,000 km). The question arises: when is engine repair required? The answer to this question can be obtained by determining the condition of the engine by its main characteristics. The control fuel consumption is usually known for each car.
The oil consumption indicator is a less frequently published parameter. For Japanese cars, the figure of 1 liter of oil per 1000 km is known. The oil pressure in the system is individual for each engine. The engine power can be determined by the acceleration time from zero to 100 km/h or by the maximum speed. These parameters are also known for each specific car. The oil pressure in the system can be used as follows: if the oil pressure indicator light is on when the engine is running at the lowest crankshaft speed, the engine requires repair. The following recommendation is available for specific oil consumption: if the oil consumption exceeds the recommended value (1 l per 1000 km of run), the engine requires repair. Specific fuel consumption can be determined by conducting a special test. The test is carried out on a serviceable car with a full load. Before checking, all vehicle components must be warmed up (for example, 10 km mileage).The test run is carried out on a straight section of asphalt road 5 km long in both directions at the speed recommended by the manufacturer as the most economical mode (usually within 60-80 km/h). It is better to measure fuel consumption using a separate measuring tank, from which gasoline is consumed during a test drive. If the specific fuel consumption has increased by more than 15% compared to the guaranteed one, the engine requires repair (under normal conditions in winter, fuel consumption increases by about 10%). The degree of reduction in engine power can be determined by the acceleration time to 100 km/h or by the maximum speed. A significant reduction in power indicates the need for engine repair.