Firstly, pressure. Everyone knows that the oil pressure in the engine should be constantly monitored while the car is moving using standard devices - a control lamp or also an electric pressure gauge.
The pressure must be at least 0.5 Bar at minimum idle speed (the control lamp does not light or flashes) and no more than 4.5 Bar at high engine speed. If the emergency oil pressure indicator lamp suddenly lights up while the engine is running 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 with a standard pressure gauge screwed into place of the sensor. If you don't have one at hand – for example, if the breakdown occurred on the road – you need to check if there is oil left in the engine sump, and then – if the conductor coming from the pressure sensor has broken. If the wire is in place and there is oil on the dipstick – unscrew the pressure sensor and, having closed the opening of the main oil line, ask an 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 conversation. The main thing to remember is that engine operation without adequate oil pressure is prohibited! It will be cheaper to get to the service station by tow. If, after starting the engine, oil flows out of the main line under pressure, then the indicating system is faulty.
Checking the functionality of the indicating device
With the ignition on, disconnect the wire from the sensor and touch it to the vehicle's ground. If the device is working properly, the needle will move to the maximum pressure value or the control lamp will light.
Checking the performance of the pressure sensor
Unscrew the sensor, press its body to the "ground" without removing the conductor. Use a pump or compressor for pumping up the wheels to create pressure in the oil line of the sensor and, with the ignition on, observe the deflection of the arrow. If the arrow of the electric oil pressure gauge deflects proportionally to the change in air pressure, then the indicating system is in good working order. If the indicating system is faulty, you can only drive to the nearest service station, provided that you have made sure that there is pressure in the lubrication system.
The second component is the oil level.
It is advisable to check the oil level daily, at least every 500 km. When the engine is cold, the level should be between the "min" and "max" marks. Deviation beyond these limits is unacceptable.
(The original is published on the website: toyotaman.ru)
Changing the oil level is an important diagnostic parameter. If, for example, in a Zhiguli it is necessary to add no more than 0.5 m of oil per 1000 km of run, then the engine condition is excellent. The standard consumption for these engines is up to 0.8 l per 1000 km, with a significantly higher consumption - look for the cause. Most often, this is a leak in the lubrication system, wear of the sealing elements of the valve timing mechanism (seals, valve guide bushings), malfunction of the crankcase ventilation system or wear of the cylinder-piston group.
That is, the faster the oil level decreases, the worse the engine condition. In this case, oil has to be topped up. Never mix different oils, even the most famous brands - this can have undesirable consequences. You can switch to another brand (company), but before that, flush the engine and then use only this brand of oil.
Sometimes the level does not decrease, but on the contrary, 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 are extremely 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 ventilation tube is formed during short trips in the cold season and is not a sign of engine malfunction. During long-term 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 a smell of fuel, then the reason is low-quality fuel, non-working spark plugs or a malfunction of 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 a high-quality motor oil is one that meets the viscosity index and quality indicators of a specific engine.
Externally, fresh oil should be yellow or light brown without any sediment. And what to do with the sediment, if it is in the branded canisters: mix thoroughly and pour into the engine, or pour only the light part of the oil, leaving the sediment (by the way, this question often came up in readers' letters)? Neither!!! Just do not buy oil with sediment. Its presence is an indicator of poor quality oil. Sediment of gray, yellow colors or their shades is formed in the presence of water. Sediment of dark to black colors appears when the oil shelf life is exceeded (that is, over 5 years) or due to poor quality purification of the base oil.
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. You need to pour half a test tube of oil, heat it to a temperature of 100°C. The appearance of a drop on the surface of the oil indicates the presence of water in it.
The presence of mechanical impurities can be roughly determined by dropping oil on filter paper. If a light yellow spot remains after drying, the oil is clean. If it 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 has already worked in the engine should be replaced when, upon inspection, the gray spot in the middle is less than the width of the black edge around its perimeter.
The most difficult test is to check for additives in the oil. To do this, you need to collect 50-70 g of oil and the same amount of distilled water in a clean, dry, heat-resistant glass container, in which 3-4 g of phenolphthalein is dissolved. Then place the container with the oil and phenolphthalein solution in a saucepan with water, heat until boiling, stirring the mixture from time to time. After the water boils, let the whole "bath" cool to room temperature. If the aqueous solution in the oil turns reddish (crimson), then there are additives, the oil is normal. In all other cases, the oil is of poor quality, without additives.