First of all, most automobile maintenance manuals only require the grade and viscosity of oil. Take Toyota Corolla as an example. In addition to the original engine oil, products of SL grade or above with viscosities of 0W-20, 5W-20 and 5W-30 can also be used.
Oil manufacturers also said that it can be adjusted, and some oil manufacturers also said that their oil can be adjusted with other brands of oil. Mobil online customer service said that under the premise of no compatibility problems, under some special circumstances, different brands of engine oils can be mixed. In fact, when developing new products, engine oil must pass the "oil compatibility" test if it wants to obtain the API gravity (API) certification or the certification of the International Lubricating Oil Standardization and Certification Committee.
There are similar tests in China. Industry standard SH/T 080 1-2007 Determination of Homogeneity and Miscibility of Engine Oil. It is required that the test oil and reference oil can form a uniform mixture after mixing, and will not separate into two phases after a series of temperature changes. The two oils must be completely compatible after mixing. No matter which part of the mixture is extracted, its component content ratio should remain unchanged.
Why are oils compatible?
The reason why different brands of engine oils are compatible with each other is mainly because the main components of engine oils are similar, which are a base oil, a foundation and various additives.
Generally speaking, the base oil accounts for 80% to 90% in the formula of engine oil, and the remaining 10% to 20% is various additives. Generally speaking, there is no difference in the base oil used for engine oil with similar price. Different brands, due to different emphasis, do have differences in the use of additives, which are generally four categories.
The most basic performance is divided into: detergent, dispersant, antiwear agent and antioxidant. If the manufacturer wants to keep the oil cleaning ability for a longer time, it may add a little more detergent. If you feel that the wear resistance is not enough, add a little anti-wear agent. Afraid of premature oxidation of engine oil, add more antioxidants, and you will know what it is for by listening to the name.
Does it matter to change it every time?
The mixing of engine oil may have a little effect on performance. Different brands of engine oils are indeed compatible, but strictly speaking, because of the different additives used, the probability of chemical reaction is very small. There is a paper in Lubricating Oil magazine, which studies the role and application of colloidal solvents in improving the function of lubricating oil detergent.
It is mentioned that calcium alkyl salicylate and calcium sulfonate are common engine oil detergents, but when these two detergents are mixed at different blending temperatures, precipitation will occur. At this time, the oil performance may be affected. When changing oil during maintenance, there is not much residual old engine oil, but in fact, the impact on our family car is still relatively small.
A friend said: ordinary gravity oil drainage can't be cleaned. It fell off when it was unscrewed, and some of it was inside. That's true, but the residual oil in the engine is not as much as we thought. It's actually quite small mixed with new engine oil.
The technical manager of Castrol China Technology Center once mentioned that the internal structure of the manual engine is complicated when the old engine oil is drained, and it is impossible to completely drain the engine oil with a daily displacement of about 200 ~ 300m·m ... A 4-cylinder engine with a displacement of 2.0L generally needs about 4L for each oil change. At this time, the ratio of old oil to new oil is actually 15: 1 or even 20: 1. In this case, the influence of old oil on new oil is actually quite limited.
It is also mentioned in the instructions for the use of Shell lubricating oil that when replacing oil products with different brands, grades and viscosities, it is usually not necessary to clean the engine, and the waste oil can be discharged directly.
If oil manufacturers dare to say so, there will certainly be no adverse reactions. Therefore, we don't have to worry too much when we are in maintenance, even if we change the new engine oil brand. Just change it to something comfortable and affordable for your own use. Generally speaking, even if you change the oil every time and change a different brand, it is actually completely possible.