An engine, like any other device, has three time intervals during which it goes through the running-in stage, the normal operation stage and the aging stage. Depending on the service life and operating conditions, the main characteristics of the engine undergo changes due to the processes occurring in the engine. The main characteristics of the engine, by which its condition can be assessed without disassembling, are engine power, specific fuel consumption, specific oil consumption and oil pressure in the system. At the engine break-in stage, the elements run-in, and this causes a slightly increased specific fuel and oil consumption and a slightly reduced oil pressure in the system. The break-in period is usually set at 1000 km, but the running-in process practically continues and ends after about 5000 km. By the end of the break-in period, the specific fuel and oil consumption decreases slightly, and the oil pressure in the system increases slightly. During the break-in period, it is recommended to avoid high loads and pay special attention to the engine lubrication system.
After the completion of the running-in process, the stage of normal operation begins, the duration of which depends not only on the design features of the engine and the vehicle in the chain, but also on the operating conditions and the degree of compliance with the basic requirements for vehicle maintenance. During this period, engine power, specific fuel and oil consumption and oil pressure in the system are maintained at approximately the same level, and vehicle operation does not cause any particular problems. The duration of the trouble-free operation period is up to a mileage of 60-80 thousand km.
During operation, due to natural wear and tear, the gaps in the connections of moving engine elements increase, the oil pressure in the system drops slightly, and the specific consumption of fuel and oil increases. These processes occur most intensively at the end of the engine warranty period (for Japanese cars during 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 based on its main characteristics. The reference fuel consumption is usually known for each vehicle.
The oil flow reference is a less frequently published parameter. For Japanese cars, the known figure is 1 liter of oil per 1000 km. The oil pressure in the system is individual for each engine. Engine power can be determined by the acceleration time from standstill to 100 km/h or by the maximum speed. These parameters are also known for each specific car. You can use the oil pressure in the system as a guide: if the oil pressure indicator light comes on when the engine is running at the lowest engine speed, the engine requires repair. There is the following recommendation for specific oil consumption: if oil consumption exceeds the recommended value (1 l per 1000 km), the engine requires repair. Specific fuel consumption can be determined by performing a special test. The test is carried out on a working vehicle with a full load. Before checking, all components of the car must be warmed up (for example, running 10 km).The test drive is made on a straight section of asphalt road 5 km long in two 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 engine power reduction can be determined by the acceleration time to 100 km/h or by the maximum speed. A significant decrease in power indicates the need for engine repair.