First, pressure. Everyone is well aware that the oil pressure in the engine must be constantly monitored while the car is moving using standard instruments - a warning lamp or also an electric dial gauge.
The pressure must be at least 0.5 bar at minimum idle speed (control lamp does not light or flashes) and not more than 4.5 bar at high engine speed. If, while the engine is running, the emergency oil pressure warning lamp suddenly lights up or the electric pressure gauge needle drops to zero, immediately turn off the engine, stop in a safe place and find the cause of this phenomenon.
The presence of pressure in the lubrication system is best checked using a standard pressure gauge screwed into place of the sensor. If this is not at hand - for example, a breakdown occurred on the road, then it is necessary to check whether there is oil left in the engine sump, and then whether the conductor coming from the pressure sensor has broken. When both the wire is in place and there is oil on the dipstick, unscrew the pressure sensor and, having closed the hole in the main oil line, ask the assistant to start the engine. If, when the engine is running, oil does not flow out of the main oil line under pressure, it is necessary to check and repair the pump drive or oil intake. But this is a topic for a separate discussion. The main thing to remember is that the operation of the engine without the appropriate oil pressure is prohibited! It will be cheaper to get to the service station in tow. If, after starting the engine, oil flows out of the main line under pressure, then the indicating system is faulty.
Checking the performance of the indicating device
With the ignition on, disconnect the wire from the sensor and touch it to "masses" car. If the device is working, the arrow will deviate to the maximum pressure value or the control lamp will light up.
Checking the performance of the pressure sensor
Unscrew the sensor, press its housing against "mass", without removing the conductor. Use a pump or compressor to inflate the wheels to pressurize the oil line of the sensor and, with the ignition on, observe the deviation of the arrow. If the arrow of the electric oil pressure gauge deviates in proportion to the change in air pressure, then the indicating system is working. With a faulty indicating system, you can only drive to the nearest service station, provided that you are convinced that there is pressure in the lubrication system.
The second component is the oil level.
It is advisable to check the oil level daily, in any case, at least after 500 km of run. On a cold engine, the level should be between the marks "min" And "max". Deviation beyond these limits is not allowed.
Changing the oil level is an important diagnostic parameter. If, for example, in "Zhiguli" it is necessary to add no more than 0.5 m of oil per 1000 km of run, then the engine is in excellent condition. The standard consumption for these engines is up to 0.8 liters per 1000 km, with a much higher consumption - look for the cause. Most often, this is a leak in the lubrication system, wear of the sealing elements of the gas distribution mechanism (seals, valve guides), malfunction of the crankcase ventilation system or wear of the cylinder-piston group.
That is, the faster the oil level decreases, the worse the condition of the engine. In this case, the oil must be topped up. Never mix different oils, even the most famous brands - this can have undesirable consequences. Switch to another brand (firm) you can, but before that, flush the engine and use only this brand of oil in the future.
Sometimes the level does not decrease, but rather increases. This is a bad sign, since the oil level can increase only in two cases: when coolant or fuel appears in the engine sump. Both of these are highly undesirable.
The appearance of a yellow-whitish foamy emulsion on the dipstick indicates the presence of coolant in the oil and, as a rule, the need for engine repair. The same emulsion in the filler neck, under the timing cover or in the crankcase vent tube is formed during short trips in the cold season and is not a sign of an engine malfunction. During prolonged operation of the engine in normal temperature conditions, this phenomenon is not observed, that is, the emulsion disappears on its own under the influence of high temperature.
If the oil level has increased significantly, it has become liquid with the smell of fuel, then the reason is poor-quality fuel, broken candles, or a malfunction in the fuel supply system. It is necessary to change the oil, but first find and eliminate the cause of the increase in its level.
And the third component is the quality of the oil.
It is clear that such a motor oil is of high quality, which corresponds in terms of viscosity index and quality indicators to a particular engine.
Outwardly fresh oil should be yellow or light brown without any precipitation. And what to do with the sediment if it is in branded canisters: carefully mix and pour into the engine, or fill in only the light part of the oil, leaving a sediment (By the way, this question often came up in letters from readers)? Neither one nor the other!!! Just don't buy oil that has sediment. Its presence is an indicator of low-quality oil. A precipitate of gray, yellow colors or their shades is formed in the presence of water. A precipitate of dark to black colors appears when the shelf life of the oil is exceeded (i.e. more than 5 years) or if the base oil is not properly refined.
The sediment can be seen if the canister is translucent and has been standing still for a long time. In all other cases, the presence of water in the oil and, therefore, its unsuitability for use in the engine, can be determined very simply and quickly. It is necessary to pour half a tube of oil, heat it to a temperature of 100°C. The appearance of exchange on the surface of the oil indicates the presence of water in it.
The presence of mechanical impurities can be approximately determined by dropping oil on the filter paper. If a light yellow stain remains after drying, the oil is clean. If there is a yellowish or, even worse, grayish spot with a dark edge around the perimeter, the oil has a large amount of mechanical impurities. This is the case if you buy fresh, new oil. And the one that already worked in the engine should be replaced when, when checking, the gray spot in the middle is less than the width of the black edging along its perimeter.
The most difficult is to check for the presence of additives in the oil. To do this, it is necessary to collect 50–70 g of oil and the same amount of distilled water in which 3–4 g of phenolphthalein are dissolved in a clean, dry, heat-resistant glass dish. Then a container with oil and a solution of phenolphthalein is placed in a saucepan with water, heated to a boil, stirring the mixture from time to time. After boiling water, give all "bath" cool down to room temperature. If the aqueous solution in oil turns reddish (crimson) - then there are additives, the oil is normal. In all other cases, the oil is of poor quality, without additives.