For many drivers the choice of engine oil is not an easy task. Someone appeals for advice to friends or online forums, and someone simply trusts the choice to specialists of service stations. We have collected popular questions from motorists on this topic and asked the experts.
How to choose the right oil, focusing on the variety of tolerances of car manufacturers and viscosity of engine oils. But it’s not as complicated as it seems at first sight, if you just focus on the recommendations of the car manufacturer, which, in turn, are based on two main points: engine type and ambient temperature.
In frosty conditions everything is clear: with too viscous oil the starter will not turn the motor and the pump will not be able to pump oil. And the smaller the first number in the designation, the less engine wear during startup. This parameter has no effect on the operation of a heated motor.
At high temperatures, the picture is more complicated. It would seem that the higher the viscosity, the better. But this is not the case. If you pour into the motor of an ordinary passenger trap “six dozen”, not intended for it at all, it is likely that you will not only lose power, but also destroy the engine. But why? After all, viscous oil should better protect the parts from wear and tear. The higher the viscosity, the thicker the oil layer in the bearings and under the piston rings, and therefore the lower the wear rate.
There are two figures in the SAE oil viscosity designation. The first one, next to the letter W, denotes low-temperature viscosity (0W, 5W, 10W, 15W, 20W). The lower this figure, the lower temperature can be used to start the engine. In the middle band, a viscosity grade of 5W-X is sufficient, but in areas of the Far North where the temperature can drop below -30° C, we recommend using oil with viscosity grade 0W-X.
The second figure in the viscosity grade designation is high-temperature viscosity (8, 12, 16, 16, 20, 20, 30, 40, 50, 60). Engines of different car manufacturers have very different requirements to this parameter. Some are structurally designed for low-viscosity oils, such as Japanese and Korean cars. And some, on the contrary, require oils with viscosity XW-40. In any case, when choosing the viscosity grade, one should follow the recommendations of the car manufacturer.
HOW DO YOU UNDERSTAND “COMPLIANCE” AND “APPROVAL”?
Car manufacturers can have a variety of oil requirements. European and American manufacturers often have their own oil tolerances and only allow their engines to be filled with products that have been approved and tested in independent or in-house laboratories. Japanese, Chinese and Korean car manufacturers do not have their own engine oil tolerances, but require compliance with the international classification API or ILSAC.
To obtain the car manufacturer’s approval, it is necessary to conduct a number of bench and motor tests in independent laboratories. Based on successful testing, an oil tolerance is issued to confirm the level of performance properties and the car company enters the oil into the list of officially approved oils. Having an official approval from the car manufacturer guarantees the correct operation of the oil in the engine. If any failure does occur and it was the oil declared as approved that caused it, the car manufacturer must compensate for the repair costs.
FIRST FILL AND SERVICE FILL
The first oil in the engines of cars is filled on the assembly line and, as a rule, the requirements that automakers have to it are higher than the oils of service filling. Such oils have a lower viscosity, so as not to unnecessarily hinder the “smoothing” of rubbing surfaces during running-in and bench tests of the engine. After the engine has been run-in, it is sent to the assembly line with the oil filled in.
The oil that enters the engine during warranty service is commonly referred to as service fill oil. Many believe that it is necessary to use only original engine oils in containers with the label of the car manufacturer. However, it should be noted that now no car company is engaged in independent oil production, but resorts to specialized companies. That is why the oil in the original packaging differs only in its logo on the label and inflated price tag. Accordingly, when changing the oil, you can use a product of any brand with the necessary tolerance and level of performance recommended by the car manufacturer in the car operating manual.
OIL IN THE POST-WARRANTY PERIOD
In the post-warranty period, when the mileage of a car can reach more than 100-200 thousand km, the gaps between the cylinder wall and the piston are increased first of all. If we continue to use low-viscosity oils, the created thickness of the oil film may be insufficient, and there will be a burst of combustion gases in the oil sump. In this regard, it makes sense to switch to more viscous oils, which will provide greater thickness of the oil film and prolong engine life.
HOW OFTEN SHOULD I CHANGE THE OIL?
The question “When to change oil?” cannot be answered unambiguously, as this moment depends on a great number of factors – from operating conditions to fuel quality. As a rule, the car operating manual contains a few underestimated figures – up to 15 thousand km. In fact, quality oils from large companies, which have official approvals of car manufacturers, may well last much longer. Therefore, nothing terrible will happen if you tighten it by 500-1000 km with oil change. But you still shouldn’t do it, because in case of breakage the car manufacturer has the right to refuse the warranty repair.
So, in order to choose the right motor oil yourself, you need to do the following steps:
- Check your car’s manual and find the section with oil requirements.
- Depending on the engine type and operation mode, determine the required level of engine oil properties.
- Select an oil viscosity grade according to SAE, depending on the ambient temperature in which the vehicle is operated and the vehicle mileage.
- Choose the desired brand of oil, carefully examine the declared levels of properties, tolerances and compliance with the requirements of car manufacturers.
- If possible, check the oil manufacturer’s licenses and approvals online or request official documents.